JP7321329B1 - Adhesive sheet - Google Patents

Abstract

[Problem] To provide a pressure-sensitive adhesive sheet capable of achieving, at a high level, both suppression of a decrease in adhesive strength due to contact with oil and suppression of decrease in adhesive strength due to contact with an aqueous solvent. and a pressure-sensitive adhesive layer containing a tackifying resin. The acrylic polymer is a polymer of monomer components containing n-heptyl acrylate. The content of the tackifying resin is an amount exceeding 10 parts by weight with respect to 100 parts by weight of the acrylic polymer. The pressure-sensitive adhesive layer has a swelling degree of 100 or less with respect to ethyl acetate. [Selection drawing] Fig. 3

Description

The present invention relates to an adhesive sheet.

In general, pressure-sensitive adhesives (also referred to as pressure-sensitive adhesives; hereinafter the same) exhibit a soft solid (viscoelastic) state in a temperature range around room temperature, and have the property of adhering to adherends under pressure. Taking advantage of such properties, adhesives are used in various industrial fields such as home electric appliances, automobiles, various machines, electronic devices, etc., typically in the form of adhesive sheets containing a layer of the adhesive, and are used for bonding members and surfaces. It is widely used for purposes such as protection.

Some pressure-sensitive adhesive sheets are used for fixing members in mobile devices such as mobile phones, smart phones, tablet personal computers, and the like. Since such portable devices are used while being carried, they are exposed to secretions such as sebum and finger marks, chemicals such as cosmetics, hair styling products, moisturizing creams and sunscreens, and oils contained in foods. It's easy to do. In particular, touch-panel type mobile devices, which have become very popular in recent years, have a display/input unit whose display unit also functions as an input unit, and are operated by the user directly touching the surface of the display/input unit with a fingertip. Therefore, there are many opportunities for oil to adhere through the fingertips. In addition, some so-called wearable devices are worn and used in contact with the skin, and in such a usage pattern, there are many opportunities to be exposed to oils such as sebum and chemicals applied to the skin. Therefore, it is desirable that the pressure-sensitive adhesive sheet for use in portable devices is less likely to decrease in pressure-sensitive adhesive strength due to contact with oil. Patent Documents 1 and 2 are cited as technical documents relating to suppression of reduction in adhesive force due to contact with oil.

JP 2017-132911 A JP 2017-165977 A

2. Description of the Related Art As mobile devices become more sophisticated and functional, there is a demand for adhesive sheets used for fixing members to have higher adhesive strength. In addition, due to the heightened awareness of hygiene in recent years, there is an increasing tendency to use aqueous solvents such as water and lower alcohols to keep mobile devices clean. It is desirable that the adhesive force is less likely to decrease even when the contact is made with the adhesive. However, in the field of adhesives, there is generally a trade-off relationship between resistance to aqueous solvents and resistance to oils. Therefore, it is not easy to realize a pressure-sensitive adhesive sheet that has a high adhesive strength and shows little decrease in adhesive strength when it comes into contact with either an oil component or an aqueous solvent.

The present invention has been made in view of the above circumstances, and suppresses the decrease in adhesive force due to contact with adhesive force and oil, and suppresses the decrease in adhesive force due to contact with aqueous solvents at a high level. An object of the present invention is to provide a pressure-sensitive adhesive sheet capable of

This specification provides a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing an acrylic polymer and a tackifying resin. The acrylic polymer is a polymer of monomer components containing n-heptyl acrylate. The content of the tackifying resin in the pressure-sensitive adhesive layer is an amount exceeding 10 parts by weight with respect to 100 parts by weight of the acrylic polymer. The pressure-sensitive adhesive layer has a swelling degree of 100 or less with respect to ethyl acetate. By using an acrylic polymer containing n-heptyl acrylate as a monomer component and setting the content of the tackifying resin to more than 10 parts by weight with respect to 100 parts by weight of the acrylic polymer under the condition that the swelling degree of the pressure-sensitive adhesive layer is 100 or less. , the adhesive force can be effectively increased, and the decrease in adhesive force due to contact with oil can be suppressed. In addition, by using n-heptyl acrylate as a monomer component of the acrylic polymer, it is possible to suitably suppress a decrease in adhesive strength due to contact with an aqueous solvent. That is, according to the above configuration, it is possible to achieve a high level of both suppression of reduction in adhesive strength due to contact with adhesive strength and oil (oil resistance) and suppression of reduction in adhesive strength due to contact with aqueous solvents (water-based solvent resistance). be able to.

In some preferred embodiments, the monomer component contains 5.0% by weight or more of a carboxy group-containing monomer. A monomer component with such a composition tends to give a PSA sheet with higher adhesive strength.

In some preferred embodiments, the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer contains a combination of an isocyanate-based cross-linking agent and an epoxy-based cross-linking agent. By using an isocyanate-based cross-linking agent and an epoxy-based cross-linking agent in combination, it is possible to appropriately adjust the degree of swelling of the pressure-sensitive adhesive layer, and adhesive strength, oil resistance, and aqueous solvent resistance can all be achieved at a high level. A seat can be advantageously realized.

In some preferred embodiments, the adhesive layer contains a phenolic tackifying resin as the tackifying resin. By using a combination of an acrylic polymer containing n-heptyl acrylate as a monomer component and a phenolic tackifying resin, the adhesive force can be effectively increased.

The adhesive layer according to some preferred embodiments contains a terpene phenolic resin as the phenolic tackifying resin. By including a terpene phenol resin in the pressure-sensitive adhesive layer, the pressure-sensitive adhesive strength can be effectively increased. The content of the terpene phenol resin is preferably 20 parts by weight or more with respect to 100 parts by weight of the acrylic polymer.

In some embodiments, the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer containing the phenol-based tackifying resin preferably contains a combination of an isocyanate-based cross-linking agent and an epoxy-based cross-linking agent. By using a combination of an acrylic polymer containing n-heptyl acrylate as a monomer component, a phenol-based tackifying resin, an isocyanate-based cross-linking agent, and an epoxy-based cross-linking agent, adhesive strength, oil resistance, and aqueous solvent resistance can be improved. can be more suitably realized.

In some aspects, the weight average molecular weight (Mw) of the acrylic polymer is preferably greater than 500,000. According to this aspect, it is easy to obtain a pressure-sensitive adhesive sheet having high levels of adhesive strength, oil resistance, and aqueous solvent resistance.

PSA sheets according to some preferred embodiments have a 180-degree peel strength (adhesive strength to SUS) of 8.0 N/10 mm or more to a stainless steel plate. A pressure-sensitive adhesive sheet having such adhesiveness to SUS can exhibit high member-fixing performance.

PSA sheets according to some preferred embodiments are configured as double-sided PSA sheets. Since the double-sided pressure-sensitive adhesive sheet is used by attaching one surface and the other surface of the pressure-sensitive adhesive sheet to an adherend, respectively, oil and aqueous solvents are likely to penetrate into the adhesion interface between the adherend and the adherend. Therefore, it is particularly significant to apply the technology disclosed herein to suppress the decrease in adhesive force caused by the oil.

A pressure-sensitive adhesive sheet according to some preferred embodiments is a double-sided pressure-sensitive adhesive sheet having a resin film as a supporting substrate and the pressure-sensitive adhesive layers provided on one surface and the other surface of the supporting substrate. ing. A double-sided pressure-sensitive adhesive sheet having such a structure is advantageous from the viewpoint of workability into a desired shape and shape retention (for example, suppression of protrusion).

The pressure-sensitive adhesive sheet disclosed herein can achieve, at a high level, both pressure-sensitive adhesive strength, suppression of pressure-sensitive adhesive strength decrease due to contact with oil, and pressure-sensitive adhesive strength decrease due to contact with an aqueous solvent. It is suitable for fixing members in devices (for example, mobile electronic devices such as smartphones). Therefore, according to this specification, a portable device using any one of the adhesive sheets disclosed herein, in other words, a portable device including the adhesive sheet is provided.

1 is a cross-sectional view schematically showing the configuration of a pressure-sensitive adhesive sheet according to one embodiment; FIG. FIG. 3 is a cross-sectional view schematically showing the configuration of a pressure-sensitive adhesive sheet according to another embodiment; FIG. 3 is a cross-sectional view schematically showing the configuration of a pressure-sensitive adhesive sheet according to another embodiment; 1 is a front view schematically showing an example of a portable device (portable electronic device) including an adhesive sheet; FIG.

Preferred embodiments of the present invention are described below. Matters other than the matters specifically mentioned in the present specification, which are necessary for the implementation of the present invention, are based on the teaching of the implementation of the invention described in the present specification and the common general knowledge at the time of filing. can be understood by those skilled in the art. The present invention can be implemented based on the contents disclosed in this specification and common general technical knowledge in the field. Further, in the following drawings, members and portions having the same function may be denoted by the same reference numerals, and redundant description may be omitted or simplified. In addition, the embodiments described in the drawings are schematic for clearly explaining the present invention, and do not necessarily accurately represent the size and scale of the pressure-sensitive adhesive sheet of the present invention that is actually provided as a product. .

As used herein, the term “adhesive” refers to a material that exhibits a soft solid (viscoelastic) state in a temperature range around room temperature and has the property of easily adhering to an adherend under pressure, as described above. . The adhesive used herein generally has a complex tensile elastic modulus E ^* (1 Hz) It may be a material having properties satisfying <10 ⁷ dyne/cm ² (typically, a material having the above properties at 25°C).

In this specification, biomass-derived carbon means carbon derived from biomass materials, ie materials derived from renewable organic resources (renewable carbon). The biomass material is typically a material derived from biological resources (typically photosynthetic plants) that can be sustainably reproduced in the presence of sunlight, water, and carbon dioxide. Say. Therefore, materials derived from fossil resources that are depleted by use after mining (fossil resource-based materials) are excluded from the concept of biomass materials here. The biomass-carbon ratio of the pressure-sensitive adhesive layer and pressure-sensitive adhesive sheet, that is, the ratio of biomass-derived carbon to the total carbon contained in the pressure-sensitive adhesive layer and pressure-sensitive adhesive sheet, is measured according to ASTM D6866 and contains a carbon isotope with a mass number of 14. can be estimated from quantity.

<Structure of Adhesive Sheet>
The adhesive sheet disclosed here includes an adhesive layer. The pressure-sensitive adhesive sheet is, for example, a substrate-less double-sided pressure-sensitive adhesive sheet comprising a first pressure-sensitive adhesive surface configured by one surface of the pressure-sensitive adhesive layer and a second pressure-sensitive adhesive surface configured by the other surface of the pressure-sensitive adhesive layer. can be of the form Moreover, the pressure-sensitive adhesive sheet disclosed herein may be in the form of a pressure-sensitive adhesive sheet with a substrate in which the pressure-sensitive adhesive layer is laminated on one or both sides of a supporting substrate. Hereinafter, the supporting substrate may be simply referred to as "substrate". Note that the concept of the adhesive sheet as used herein can include what is called an adhesive tape, an adhesive label, an adhesive film, and the like. The pressure-sensitive adhesive sheet disclosed herein may be roll-shaped or sheet-shaped. Alternatively, it may be a pressure-sensitive adhesive sheet processed into various shapes.

FIG. 1 schematically shows the structure of a pressure-sensitive adhesive sheet according to one embodiment. This pressure-sensitive adhesive sheet 1 is configured as a substrate-less double-sided pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer 21 . The adhesive sheet 1 has a first adhesive surface 21A configured by one surface (first surface) of the adhesive layer 21 and a second adhesive surface configured by the other surface (second surface) of the adhesive layer 21. 21B are attached to different parts of the adherend. The locations where the adhesive surfaces 21A and 21B are attached may be locations on different members or different locations within a single member. As shown in FIG. 1, the pressure-sensitive adhesive sheet 1 before use (that is, before being attached to an adherend) has a first pressure-sensitive adhesive surface 21A and a second pressure-sensitive adhesive surface 21B that are peeled off at least on the side facing the pressure-sensitive adhesive layer 21. It can be a constituent element of the PSA sheet 100 with a release liner in a form protected by the release liners 31 and 32 which are surfaces. As the release liners 31 and 32, for example, one having a sheet-like base material (liner base material) provided with a release layer by a release treatment agent on one side so that the one side becomes a release surface is preferably used. obtain. Alternatively, the release liner 32 is omitted, and a release liner 31 having release surfaces on both sides is used. A release liner-attached pressure-sensitive adhesive sheet in a form (roll form) protected by contacting the back surface of the adhesive sheet may be configured.

FIG. 2 schematically shows the structure of a pressure-sensitive adhesive sheet according to another embodiment. The pressure-sensitive adhesive sheet 2 includes a sheet-like support base material (for example, a resin film) 10 having a first surface 10A and a second surface 10B, and a base material provided with an adhesive layer 21 provided on the first surface 10A side. It is configured as a single-sided adhesive sheet with The pressure-sensitive adhesive layer 21 is fixedly provided on the first surface 10A side of the supporting substrate 10 , that is, without the intention of separating the pressure-sensitive adhesive layer 21 from the supporting substrate 10 . In the pressure-sensitive adhesive sheet 2 before use, as shown in FIG. 2, the surface (adhesive surface) 21A of the pressure-sensitive adhesive layer 21 is protected by a release liner 31 having a release surface on at least the side facing the pressure-sensitive adhesive layer 21. It can be a component of the pressure-sensitive adhesive sheet 200 with a release liner. Alternatively, by omitting the release liner 31 and using the supporting substrate 10 whose second surface 10B is the releasing surface, the adhesive sheet 2 is wound so that the adhesive surface 21A becomes the second surface (back surface) of the supporting substrate 10. ) 10B may be in a protected form (roll form).

FIG. 3 schematically shows the structure of a pressure-sensitive adhesive sheet according to still another embodiment. This adhesive sheet 3 consists of a sheet-like supporting substrate (for example, a resin film) 10 having a first surface 10A and a second surface 10B, and a first adhesive layer 21 fixedly provided on the first surface 10A side. and a second adhesive layer 22 fixedly provided on the second surface 10B side. The pressure-sensitive adhesive sheet 3 before use has a surface (first pressure-sensitive adhesive surface) 21A of the first pressure-sensitive adhesive layer 21 and a surface (second pressure-sensitive adhesive surface) 22A of the second pressure-sensitive adhesive layer 22 as shown in FIG. , 32 can be a component of the pressure-sensitive adhesive sheet 300 with a release liner. Alternatively, the release liner 32 is omitted, and a release liner 31 having release surfaces on both sides is used. A release liner-attached pressure-sensitive adhesive sheet in a form (roll form) protected by contacting the back surface of the adhesive sheet may be configured.

In the double-sided pressure-sensitive adhesive sheet with a substrate, if at least one pressure-sensitive adhesive layer (for example, the first pressure-sensitive adhesive layer) of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer is the pressure-sensitive adhesive layer described below. Well, the other pressure-sensitive adhesive layer (for example, the second pressure-sensitive adhesive layer) may be the pressure-sensitive adhesive layer disclosed herein, and the pressure-sensitive adhesive layer disclosed herein (specifically, the one pressure-sensitive adhesive layer The adhesive layer may have a composition different from that of the layer, eg the first adhesive layer. Such other pressure-sensitive adhesive layer may be formed from, for example, a known or commonly used pressure-sensitive adhesive.

<Adhesive layer>
The pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive sheet disclosed herein contains an acrylic polymer and a tackifying resin. The pressure-sensitive adhesive layer is typically a pressure-sensitive adhesive layer having the acrylic polymer as a base polymer. Such an adhesive layer is also called an acrylic adhesive layer. The base polymer of the pressure-sensitive adhesive layer refers to the main component of the rubber-like polymer (polymer exhibiting rubber elasticity in a temperature range around room temperature) contained in the pressure-sensitive adhesive layer. In this specification, the term "main component" refers to a component contained in an amount exceeding 50% by weight unless otherwise specified. In addition, the following descriptions of components that can be included in the adhesive and adhesive layer are also applicable to the adhesive composition used to form the adhesive (layer), unless otherwise specified.

In the present specification, the term "acrylic polymer" refers to a polymer containing monomer units derived from a monomer having at least one (meth)acryloyl group in one molecule as the monomer units constituting the polymer. . Hereinafter, a monomer having at least one (meth)acryloyl group in one molecule is also referred to as "acrylic monomer". Accordingly, an acrylic polymer in this specification is defined as a polymer containing monomeric units derived from an acrylic monomer. In this specification, "(meth)acryloyl" is meant to comprehensively refer to acryloyl and methacryloyl. Similarly, "(meth)acrylate" is a generic term for acrylate and methacrylate, and "(meth)acrylic" is generic for acrylic and methacrylic.

(acrylic polymer)
As the acrylic polymer used in the technique disclosed herein, a polymer of monomer components containing n-heptyl acrylate (n-HpA) is used. The inventors have found that an acrylic polymer polymerized using a monomer component containing n-HpA (that is, an alkyl acrylate having an n-heptyl group at the ester end) is obtained by replacing the n-HpA with n-butyl acrylate (BA). and 2-ethylhexyl acrylate (2EHA), etc. Adhesive that achieves a high level of both adhesive strength, oil resistance, and aqueous solvent resistance compared to acrylic polymers polymerized using monomer components that have been replaced with other alkyl acrylates. It has been found to be suitable for realization of sheets. More specifically, for example, compared to a configuration in which n-HpA is replaced with 2EHA, it is easier to improve adhesive strength while suppressing the degree of swelling. good resistance to The reason for this is not particularly limited, but the polymer containing n-HpA as a monomer unit has a low glass transition temperature, so that the pressure-sensitive adhesive layer can be well adhered to the adherend, and the adhesion of the two can be improved. In addition to easily suppressing the penetration of oil and aqueous solvents into the interface, it has a relatively long linear side chain derived from n-HpA, so it has good compatibility with tackifying resins, so tackification Even if the resin content is increased, it is easy to suppress the decrease in adhesive strength due to contact with oil, and the side chain derived from n-HpA has more carbon atoms than the side chain derived from alkyl acrylate. This is probably because the degree of swelling is easily suppressed because of its low oiliness. In addition, since the side chain derived from n-HpA is less hydrophilic than the side chain derived from an alkyl acrylate having a smaller number of carbon atoms (eg, BA), an aqueous solvent (eg, a mixed solvent of water and a lower alcohol ), it is thought that it is easy to suppress the decrease in adhesive strength due to contact with.

In some embodiments, the proportion of n-HpA in the monomer component of the acrylic polymer is suitably 50% by weight or more (for example, more than 50% by weight), preferably 70% by weight or more, more preferably 80 wt% or more, more preferably 85 wt% or more, particularly preferably 90 wt% or more, may be 91 wt% or more, may be 92 wt% or more, may be 94 wt% or more, or may be 94.5 wt% or more It's okay. By increasing the amount of n-HpA used, the effect of use tends to be more effectively exhibited. In some embodiments, the proportion of n-HpA in the monomer component may be 98 wt% or greater, or 99 wt% or greater, or 100 wt%. On the other hand, from the viewpoint of facilitating control of the degree of swelling of the pressure-sensitive adhesive layer and facilitating adjustment of the balance of properties, in some embodiments, the proportion of n-HpA in the monomer component is 99.5% by weight or less. is preferably 97% by weight or less (for example, less than 97% by weight), more preferably 96% by weight or less, still more preferably 95% by weight or less, and may be 94% by weight or less, or 93% by weight or less. or 91% by weight or less.

The acrylic polymer may be copolymerized with an alkyl (meth)acrylate other than n-HpA (hereinafter also referred to as “optional alkyl (meth)acrylate”). As an arbitrary alkyl (meth)acrylate, for example, a compound represented by the following formula (1) can be preferably used.
_CH2 =C( ^R1 ) ^COOR2 (1)
Here, R ¹ in the above formula (1) is a hydrogen atom or a methyl group. R ² is a chain alkyl group having 1 to 20 carbon atoms (excluding n-heptyl group).

Examples of the above optional alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s - butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl methacrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl ( meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate Acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate and the like. These arbitrary alkyl (meth)acrylates can be used singly or in combination of two or more. Optional alkyl (meth)acrylates that may be preferably used include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA). These arbitrary alkyl (meth)acrylates can be used singly or in combination of two or more.

In some embodiments, the proportion of any alkyl (meth)acrylate contained in the monomer component (the total proportion thereof when two or more are used) is 50 wt. % (for example, 49.5% by weight or less), preferably less than 47% by weight, more preferably 45% by weight or less, even more preferably 40% by weight or less, and may be 30% by weight or less. , 10% by weight or less, 5% by weight or less, or 1% by weight or less. For the optional alkyl (meth)acrylate in which R ² in the above formula (1) is an alkyl acrylate having 8 or more carbon atoms or an alkyl methacrylate having 7 or more carbon atoms, the above optional alkyl (meth)acrylate contained in the monomer component From the viewpoint of oil resistance, etc., the proportion (the total proportion thereof when two or more are used) is suitably 30% by weight or less, preferably 20% by weight or less, and more preferably 10% by weight or less. Yes, it may be 5% by weight or less, 1% by weight or less, or 0.5% by weight or less. In addition, for the optional alkyl (meth)acrylate in which R ² in the above formula (1) is an alkyl (meth)acrylate having 6 or less carbon atoms, the ratio of the optional alkyl (meth)acrylate contained in the monomer component (2 types When using the above, the total ratio thereof) is suitably 30% by weight or less, preferably 20% by weight or less, more preferably 10% by weight or less, of the monomer component from the viewpoint of resistance to aqueous solvents. Yes, it may be 5% by weight or less, 1% by weight or less, or 0.5% by weight or less. In some embodiments, the techniques disclosed herein can be preferably practiced in embodiments in which the monomer component is substantially free of any alkyl (meth)acrylate.

In this specification, the expression that the monomer component does not substantially contain the monomer A (e.g., the above optional alkyl (meth)acrylate) means that the monomer A is not used at least intentionally, and the monomer A is For example, unintentional inclusion of about 0.01% by weight or less is permissible.

In some embodiments, the monomer component may include an alkyl (meth)acrylate having a biomass-derived alkyl group at the ester end (hereinafter also referred to as “biomass alkyl (meth)acrylate”). In recent years, environmental problems such as global warming have come to be emphasized, and it is desired to reduce the amount of fossil resource-based materials such as petroleum used. Under such circumstances, it is required to reduce the amount of fossil resource-based materials used in the field of pressure-sensitive adhesives as well. By using biomass alkyl (meth)acrylate, it is possible to suitably realize an acrylic pressure-sensitive adhesive that takes into consideration the suppression of dependence on fossil resource-based materials.

The biomass alkyl (meth)acrylate is not particularly limited, and is, for example, an ester of a biomass-derived alkanol and a biomass-derived or non-biomass-derived (meth)acrylic acid. Examples of biomass-derived alkanols include biomass ethanol, alkanols derived from plant sources such as palm oil, palm kernel oil, coconut oil, castor oil, and the like. When the number of carbon atoms in the biomass-derived alkanol is 3 or more, the alkanol may be linear or branched. In some embodiments, an ester of a biomass-derived alkanol and a non-biomass-derived (meth)acrylic acid is used as the biomass alkyl (meth)acrylate used to synthesize the acrylic polymer. In such a biomass alkyl (meth)acrylate, the greater the number of carbon atoms in the alkanol, the greater the ratio of the number of biomass-derived carbons to the total number of carbons contained in the biomass alkyl (meth)acrylate, that is, the biomass carbon ratio of the alkyl (meth)acrylate. becomes higher. Therefore, in the above biomass alkyl (meth)acrylate, it is desirable that the number of carbon atoms in the biomass-derived alkyl group is large in terms of reducing dependence on fossil resource-based materials. On the other hand, if the number of carbon atoms in the alkyl group constituting the alkyl (meth)acrylate is too large, it tends to swell excessively due to contact with oil, resulting in a decrease in oil resistance. It can be disadvantageous in terms of productivity. In an embodiment using an ester of a biomass-derived alkanol and a non-biomass-derived (meth)acrylic acid as the biomass alkyl (meth)acrylate, adhesive properties and reduced dependence on fossil resource-based materials (more specifically, It is desirable to use a material that satisfies both the biomass carbon ratio of the alkyl (meth)acrylate and the biomass carbon ratio of the alkyl (meth)acrylate in a well-balanced manner.

In some preferred embodiments, biomass-derived n-heptyl acrylate (biomass n-HpA) is used as the n-heptyl acrylate. By using biomass n-HpA, the effects of the technology disclosed herein can be realized while reducing dependence on fossil resource-based materials. The biomass n-HpA is an ester of a biomass-derived alkanol and a biomass-derived or non-biomass-derived acrylic acid, for example, an ester of a biomass-derived alkanol and a non-biomass-derived acrylic acid can be used. In such compounds, only the linear heptyl groups are derived from biomass.

The proportion of biomass alkyl (meth)acrylate (preferably biomass n-HpA) in the monomer component of the acrylic polymer is, for example, in some embodiments, 50% by weight or more (for example, more than 50% by weight), preferably is 70% by weight or more, more preferably 80% by weight or more, still more preferably 85% by weight or more, particularly preferably 90% by weight or more, and may be 92% by weight or more, 94% by weight or more, or 96% by weight or more It's okay. In addition, the proportion of biomass alkyl (meth)acrylate (preferably biomass n-HpA) among the monomer components is less than 97% by weight, and in some embodiments may be 95% by weight or less, or 93% by weight. It may be less than or equal to 91% by weight or less. In some other embodiments, the proportion of biomass alkyl (meth)acrylate in the monomer component may be 90% by weight or less, 70% by weight or less, 50% by weight or less, or 30% by weight or less, It may be 10% by weight or less, or 1% by weight or less.

In some aspects, the monomer component of the acrylic polymer preferably contains a carboxy group-containing monomer. Carboxy group-containing monomers can help improve adhesive strength by improving cohesiveness based on their polarity, suppress excessive swelling of the adhesive layer against oil, and suppress reduction in adhesive strength due to contact with oil (for example, It can contribute to the improvement of the adhesive strength maintenance rate _RA ). Moreover, since the carboxyl group can become a cross-linking point of the acrylic polymer, there is an advantage that the degree of swelling of the pressure-sensitive adhesive layer can be easily adjusted.

Examples of carboxy group-containing monomers include acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid. be done. Preferred carboxy group-containing monomers include AA and MAA. AA is particularly preferred. A carboxy group-containing monomer can be used individually by 1 type or in combination of 2 or more types.

The ratio of the carboxy group-containing monomer in the monomer component of the acrylic polymer may be, for example, 0.5% by weight or more, 1.0% by weight or more, or 2.0% by weight or more. In some aspects, the proportion of the carboxy group-containing monomer in the monomer component of the acrylic polymer is suitably greater than 3.0 wt%, and advantageously greater than or equal to 3.5 wt%, It is preferably 4.0% by weight or more, more preferably 4.5% by weight or more or 5.0% by weight or more. By increasing the amount of the carboxy group-containing monomer used, the decrease in adhesive strength due to contact with oil tends to be better suppressed, and the degree of swelling also tends to be suppressed. In some aspects, the proportion of the carboxy group-containing monomer in the monomer component may be greater than 5.0 wt%, may be 5.5 wt% or more, or may be 6.0 wt% or more. , 7.0% by weight or more, 8.0% by weight or more (for example, more than 8.0% by weight), or 9.0% by weight or more. In addition, the amount of the carboxyl group-containing monomer is, for example, 20% by weight or less of the total monomer components, and from the viewpoint of suppressing the decrease in adhesive strength due to contact with an aqueous solvent, preferably 15% by weight or less, More preferably, it is 12% by weight or less. In some embodiments, the amount of the carboxy group-containing monomer may be less than 10 wt%, less than 9 wt%, less than 8 wt%, less than 6 wt%, less than 5 wt%. It's okay. By appropriately adjusting the amount of the carboxy group-containing monomer to be used within the above range, it is possible to achieve a good balance among adhesive strength, oil resistance, and aqueous solvent resistance.

The acrylic polymer may be copolymerized with a functional group-containing monomer other than the carboxyl group-containing monomer. Hereinafter, the functional group-containing monomer other than the carboxy group-containing monomer is also referred to as "functional group-containing monomer B". Examples of functional group-containing monomers B that can introduce functional groups that can serve as crosslinking base points into acrylic polymers or that can contribute to improving adhesive strength include hydroxyl group (OH group)-containing monomers (2-hydroxyethyl (meth)acrylate, 2- Hydroxyalkyl (meth)acrylates such as hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate; polypropylene glycol mono(meth)acrylate, etc. ), acid anhydride group-containing monomers, amide group-containing monomers ((meth)acrylamide, N,N-dimethyl(meth)acrylamide, etc.), amino group-containing monomers (aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, etc.), epoxy group-containing monomers, cyano group-containing monomers, keto group-containing monomers, monomers having a nitrogen atom-containing ring (N-vinyl-2-pyrrolidone, N-(meth)acryloylmorpholine, etc.), alkoxysilyl group-containing monomers, imide group-containing monomers, and the like. The functional group-containing monomer B may be used alone or in combination of two or more. In the embodiment in which the monomer component constituting the acrylic polymer contains the functional group-containing monomer B, the monomer component may or may not substantially contain the carboxy group-containing monomer.

When the monomer component constituting the acrylic polymer contains the functional group-containing monomer B described above, the content of the functional group-containing monomer B in the monomer component is not particularly limited. From the viewpoint of appropriately exhibiting the effect of using the functional group-containing monomer B, the content of the functional group-containing monomer B in the monomer component can be, for example, 0.1% by weight or more, and 0.5% by weight or more. 1% by weight or more. In addition, from the viewpoint of easily balancing oil resistance and aqueous solvent resistance in the monomer component containing n-HpA, it is appropriate that the content of the functional group-containing monomer B in the monomer component is 40% by weight or less. , is preferably 20% by weight or less, and may be 10% by weight or less (for example, 5% by weight or less). In some embodiments, the content of functional group-containing monomer B in the monomer component is, for example, less than 3 wt%, may be less than 1 wt%, may be less than 0.5 wt%, may be less than 0.3 wt% % or less than 0.1% by weight. The technology disclosed herein can be preferably implemented in a mode in which the monomer component of the acrylic polymer does not substantially contain the functional group-containing monomer B.

Further, when a hydroxyl group-containing monomer is used as the functional group-containing monomer B, the content thereof may be, for example, approximately 0.001% by weight or more, or may be approximately 0.01% by weight or more, based on the total monomer components. It may be about 0.02% by weight or more. Also, the content of the hydroxyl group-containing monomer is suitably about 10% by weight or less, preferably about 5% by weight or less, more preferably about 2% by weight or less, in the total monomer components. In some embodiments, the content of hydroxyl group-containing monomers in the monomer component may be, for example, less than 1 wt%, less than 0.5 wt%, less than 0.3 wt%, or less than 0.1 wt%. % or less than 0.01% by weight. The monomer component of the acrylic polymer may be substantially free of hydroxyl group-containing monomers. According to the technology disclosed herein, desired effects can be achieved without relying on hydroxyl group-containing monomers.

In an aspect in which the monomer component constituting the acrylic polymer contains a carboxy group-containing monomer, the ratio of the carboxy group-containing monomer to the total functional group-containing monomers contained in the monomer component (total functional group-containing monomers including the carboxy group-containing monomer). is suitably 30% by weight or more, preferably 50% by weight or more, more preferably 70% by weight or more, and still more preferably 80% by weight, from the viewpoint of effectively exhibiting the effect of copolymerizing the carboxy group-containing monomer. Above, particularly preferably 90% by weight or more, for example, 95% by weight or more, 97% by weight or more, 98% by weight or more, 99% by weight or more (for example, 99.9% by weight) % or more). The upper limit of the ratio of the carboxy group-containing monomer to the total functional group-containing monomer is 100% by weight, which corresponds to an embodiment in which the functional group-containing monomer B is not used. In some aspects, the ratio of the carboxy group-containing monomer to the total functional group-containing monomer may be, for example, 95% by weight or less.

The monomer component constituting the acrylic polymer may contain a copolymer component other than the functional group-containing monomer described above for the purpose of improving the cohesive force and the like. Examples of other copolymerization components include vinyl ester monomers such as vinyl acetate; aromatic vinyl compounds such as styrene; ) acrylate; aryl (meth)acrylate (e.g. phenyl (meth)acrylate), aryloxyalkyl (meth)acrylate (e.g. phenoxyethyl (meth)acrylate), arylalkyl (meth)acrylate (e.g. benzyl (meth)acrylate), etc. Aromatic ring-containing (meth)acrylates; olefinic monomers; chlorine-containing monomers; isocyanate group-containing monomers such as 2-(meth)acryloyloxyethyl isocyanate; alkoxy such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate group-containing monomers; vinyl ether-based monomers such as methyl vinyl ether and ethyl vinyl ether; The above-mentioned other copolymerization components can be used singly or in combination of two or more.

The amount of such other copolymerization component may be appropriately selected according to the purpose and application, and is not particularly limited, but from the viewpoint of appropriately exhibiting the effect of use, it should be 0.05% by weight or more in the monomer component. is suitable, and it may be 0.5% by weight or more. In addition, from the viewpoint of making it easier to achieve both oil resistance and aqueous solvent resistance in a well-balanced manner in the monomer component containing n-HpA, the content of other copolymerization components in the monomer component is preferably 20% by weight or less. Yes, preferably 10% by weight or less, more preferably 8% by weight or less, still more preferably less than 5% by weight, for example, less than 3% by weight, or less than 1% by weight. The technology disclosed herein can also be preferably practiced in a mode in which the monomer component does not substantially contain other copolymerization components.

The monomer component constituting the acrylic polymer is a polyfunctional monomer having at least two polymerizable functional groups (typically radically polymerizable functional groups) having unsaturated double bonds such as (meth)acryloyl groups and vinyl groups. may include By using a polyfunctional monomer as a monomer component, the cohesive force of the adhesive layer can be increased and the degree of swelling can be suppressed. Polyfunctional monomers are not particularly limited, and examples include 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and neopentyl glycol di(meth)acrylate. etc. A polyfunctional monomer can be used individually by 1 type or in combination of 2 or more types.

The lower limit of the amount used when using a polyfunctional monomer is not particularly limited as long as it is greater than 0% by weight. The amount of polyfunctional monomer to be used can be appropriately set so that the purpose of use of the polyfunctional monomer is achieved. Usually, by setting the amount of the polyfunctional monomer used to about 0.001% by weight or more (for example, about 0.01% by weight or more) of the monomer component, the effect of using the polyfunctional monomer can be appropriately exhibited. Further, in some aspects, the amount of the polyfunctional monomer used is suitably about 3% by weight or less of the above-mentioned monomer component from the viewpoint of facilitating obtaining good adhesive strength, and about 2% by weight or less is suitable. Preferably, about 1% by weight or less (eg, about 0.5% by weight or less) is more preferable. The monomer component that constitutes the acrylic polymer may be substantially composed of monofunctional monomers. That is, the monomer component does not have to contain a polyfunctional monomer.

The biomass carbon ratio of the monomer component constituting the acrylic polymer (biomass carbon ratio of the acrylic polymer) may be, for example, 1% or more, suitably 10% or more, preferably 30% or more, more preferably 30% or more. is 50% or more (eg, more than 50%), may be 70% or more, may be 80% or more, or may be 90% to 100%. By designing in this way, an acrylic pressure-sensitive adhesive that takes into consideration the suppression of dependence on fossil resource-based materials can be obtained.

The method for obtaining the acrylic polymer is not particularly limited, and various polymerization methods known as synthesis methods for acrylic polymers, such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization. can be adopted as appropriate. For example, a solution polymerization method can be preferably employed. As a method for supplying the monomers when carrying out solution polymerization, a batch charging method for supplying all monomer raw materials at once, a continuous supply (dropping) method, a divided supply (dropping) method, or the like can be appropriately employed. The polymerization temperature can be appropriately selected depending on the type of monomer and solvent used, the type of polymerization initiator, etc., and is, for example, about 20° C. to 170° C. (typically about 40° C. to 140° C.). can be done.

The solvent (polymerization solvent) used for solution polymerization can be appropriately selected from conventionally known organic solvents. For example, aromatic compounds such as toluene (typically aromatic hydrocarbons); acetic esters such as ethyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; 1,2-dichloroethane and the like Halogenated alkanes; lower alcohols such as isopropyl alcohol (e.g., monohydric alcohols having 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone; Any one kind of solvent or a mixed solvent of two or more kinds can be used.

The initiator used for polymerization can be appropriately selected from conventionally known polymerization initiators according to the type of polymerization method. For example, one or more azo polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN) can be preferably used. Other examples of polymerization initiators include persulfates such as potassium persulfate; peroxide-based initiators such as benzoyl peroxide (BPO) and hydrogen peroxide; substituted ethane-based initiators such as phenyl-substituted ethane; group carbonyl compounds; and the like. Still another example of the polymerization initiator is a redox initiator obtained by combining a peroxide and a reducing agent. Such polymerization initiators can be used singly or in combination of two or more. The amount of the polymerization initiator to be used may be a normal amount, for example, about 0.005 to 1 part by weight (typically about 0.01 to 1 part by weight) per 100 parts by weight of all the monomer components. degree).

The weight average molecular weight (Mw) of the acrylic polymer is not particularly limited, and may be, for example, about 300,000 or more and 5,000,000 or less. Mw of the acrylic polymer is usually preferably more than 500,000 (eg, 550,000 or more), more preferably 600,000 or more, or more than 600,000 (eg, 650,000 or more). An acrylic polymer having such an Mw makes it easy to obtain a pressure-sensitive adhesive sheet having high levels of adhesive strength, oil resistance, and aqueous solvent resistance. In some embodiments, the Mw of the acrylic polymer may be 700,000 or more, 800,000 or more, 900,000 or more or more than 900,000, 950,000 or more, 1 million or more Or it may be more than 1 million, 1.05 million or more, or 1.05 million or more, 1.15 million or more, 1.2 million or more, or 1.2 million or more. In addition, from the viewpoint of the ease of synthesizing the acrylic polymer, the ease of preparation of the pressure-sensitive adhesive composition, the coating properties, etc., the Mw of the acrylic polymer is usually about 3 million or less (for example, 2.5 million or less). Appropriate. From the viewpoint of enhancing the adhesion between the pressure-sensitive adhesive layer and the adherend and making it easier to suppress the penetration of oil and aqueous solvents into the interface between the two, in some embodiments, the Mw of the acrylic polymer is 2,000,000 or less. preferably 1.8 million or less, 1.6 million or less, 1.5 million or less, 1.4 million or less, 1.3 million or less, 1.2 million or less or less than 1.2 million, 1.10 It may be 10,000 or less, 1,000,000 or less, 900,000 or less or less than 900,000, 850,000 or less, or 750,000 or less.

The Mw of the acrylic polymer can be measured by gel permeation chromatography (GPC) and calculated as a value converted to standard polystyrene. Specifically, it can be obtained by measuring under the following conditions using a GPC measurement device with the trade name "HLC-8220GPC" (manufactured by Tosoh Corporation). The same applies to the examples described later.
[Measurement conditions of GPC]
Sample concentration: 0.2% by weight (tetrahydrofuran solution)
Sample injection volume: 10 μL
Eluent: Tetrahydrofuran (THF)
Flow rate (flow rate): 0.6 mL/min Column temperature (measurement temperature): 40°C
column:
Sample column: 1 product name “TSKguardcolumn SuperHZ-H” + 2 product name “TSKgel SuperHZM-H” (manufactured by Tosoh Corporation)
Reference column: Product name "TSKgel SuperH-RC" 1 column (manufactured by Tosoh Corporation)
Detector: differential refractometer (RI)
Standard sample: Polystyrene

(tackifying resin)
The adhesive layer disclosed herein contains more than 10 parts by weight of a tackifying resin with respect to 100 parts by weight of the acrylic polymer described above, which is a polymer of monomer components containing n-HpA. Adhesion can be effectively improved by including such an amount of tackifying resin. The content of the tackifying resin relative to 100 parts by weight of the acrylic polymer may be, for example, 12 parts by weight or more, or may be 15 parts by weight or more, or 18 parts by weight or more. In some embodiments, the content of the tackifying resin with respect to 100 parts by weight of the acrylic polymer is suitably 18.5 parts by weight or more, and is 20 parts by weight or more, from the viewpoint of obtaining a higher use effect. It is preferably 25 parts by weight or more, or 30 parts by weight or more. The acrylic polymer containing n-HpA as a monomer unit has good compatibility with the tackifying resin, so it contains more tackifying resin while maintaining cohesion suitable for suppressing deterioration of oil resistance and aqueous solvent resistance. It is possible to improve the adhesive strength. In addition, the content of the tackifying resin with respect to 100 parts by weight of the acrylic polymer may be, for example, 100 parts by weight or less or 90 parts by weight or less. Part by weight or less is suitable, preferably 60 parts by weight or less (for example, 55 parts by weight or less), more preferably 50 parts by weight or less, may be 45 parts by weight or less, may be 40 parts by weight or less, or may be 35 parts by weight or less. It may be not more than 30 parts by weight, or not more than 25 parts by weight.

The tackifying resin is not particularly limited, and examples thereof include phenol-based tackifying resins, rosin-based tackifying resins, terpene-based tackifying resins, hydrocarbon-based tackifying resins, epoxy-based tackifying resins, polyamide-based tackifying resins, Various tackifying resins such as elastomer-based tackifying resins and ketone-based tackifying resins can be used. Such tackifying resins can be used singly or in combination of two or more.

Examples of phenolic tackifier resins include terpene phenolic resins, hydrogenated terpene phenolic resins, alkylphenolic resins, rosin phenolic resins, and the like.
Terpene phenol resin refers to a polymer containing a terpene residue and a phenol residue, a copolymer of terpenes and a phenol compound (terpene-phenol copolymer resin), and a homopolymer or copolymer of terpenes is a concept that includes both phenol-modified (phenol-modified terpene resin). Specific examples of terpenes constituting such terpene phenol resins include monoterpenes such as α-pinene, β-pinene, and limonene (including d-, l- and d/l (dipentene)). is mentioned. A hydrogenated terpene phenol resin refers to a hydrogenated terpene phenol resin having a structure obtained by hydrogenating such a terpene phenol resin. It is sometimes called a hydrogenated terpene phenolic resin.
Alkylphenol resins are resins obtained from alkylphenols and formaldehyde (oily phenolic resins). Examples of alkylphenol resins include novolac and resole types.
Rosin phenolic resins are typically phenol-modified rosins or various rosin derivatives (including rosin esters, unsaturated fatty acid-modified rosins, and unsaturated fatty acid-modified rosin esters). Examples of rosin phenol resins include rosin phenol resins obtained by adding phenol to rosins or the above various rosin derivatives with an acid catalyst and thermally polymerizing them.
Among these phenolic tackifying resins, terpene phenol resins, hydrogenated terpene phenol resins and alkylphenol resins are preferred, terpene phenol resins and hydrogenated terpene phenol resins are more preferred, and terpene phenol resins are particularly preferred.

Examples of rosin-based tackifying resins include unmodified rosins (fresh rosins) such as gum rosin, wood rosin and tall oil rosin; added rosin, disproportionated rosin, polymerized rosin, and other chemically modified rosins (the same shall apply hereinafter); other various rosin derivatives; Examples of the rosin derivative include rosins obtained by esterifying unmodified rosin with alcohols (that is, esterified rosin), and esterifying modified rosin with alcohols (that is, esterified rosin). Esters; Undenatured rosin and rosins modified with unsaturated fatty acids obtained by modifying rosin with unsaturated fatty acids; Rosin esters modified with unsaturated fatty acids obtained by modifying rosin esters with unsaturated fatty acids; Unmodified rosin, modified rosin, unsaturated rosin alcohols obtained by reducing the carboxy groups in fatty acid-modified rosins or unsaturated fatty acid-modified rosin esters; metal salts of rosins (especially rosin esters) such as unmodified rosin, modified rosin, and various rosin derivatives; mentioned. Among them, rosin ester is preferred. Specific examples of rosin esters include, but are not limited to, esters of unmodified rosin or modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.), such as methyl ester, triethylene glycol ester, and glycerin ester. , pentaerythritol ester and the like.

Examples of terpene-based tackifying resins include polymers of terpenes (eg, monoterpenes) such as α-pinene, β-pinene, d-limonene, l-limonene, and dipentene. It may be a homopolymer of one kind of terpenes, or a copolymer of two or more kinds of terpenes. One type of terpene homopolymer includes α-pinene polymer, β-pinene polymer, dipentene polymer and the like.

Examples of hydrocarbon-based tackifying resins include aliphatic (C5) petroleum resins, aromatic (C9) petroleum resins, aliphatic/aromatic copolymer (C5/C9) petroleum resins, these Hydrogenates (e.g., alicyclic petroleum resins obtained by hydrogenating aromatic petroleum resins), various modified products thereof (e.g., maleic anhydride-modified products), coumarone-based resins, coumarone-indene-based resins and various other hydrocarbon-based resins.

In some embodiments, it is preferred to use a phenolic tackifying resin as the tackifying resin. By using a phenol-based tackifying resin, it is possible to preferably improve the adhesive strength while suppressing an increase in the degree of swelling. Among them, terpene phenol resin is preferable. As the tackifying resin, one or more phenolic tackifying resins may be used alone, or a phenolic tackifying resin and another tackifying resin (for example, a rosin-based tackifying resin) may be used in combination. may The ratio of the phenol-based tackifying resin (for example, terpene phenol resin) to the total tackifying resin contained in the adhesive layer can be, for example, about 35% by weight or more, and the effect of using the phenol-based tackifying resin can be preferably obtained. From the viewpoint of performance, the content is preferably more than about 50% by weight, may be about 70% by weight or more, and may be about 80% by weight or more. The technology disclosed herein is preferred in embodiments in which substantially all of the tackifying resin (e.g., approximately 97% by weight or more, or 99% by weight or more, or even 100% by weight) is a phenolic tackifying resin. can be implemented.

In the embodiment using a terpene phenol resin as the tackifying resin, the content of the terpene phenol resin may be, for example, 1 part by weight or more, 3 parts by weight or more, or 5 parts by weight with respect to 100 parts by weight of the acrylic polymer. It may be 7 parts by weight or more, 9 parts by weight or more, 12 parts by weight or more, 15 parts by weight or more, or 18 parts by weight or more. In some aspects, the content of the terpene phenol resin relative to 100 parts by weight of the acrylic polymer is suitably 18.5 parts by weight or more, and is 20 parts by weight or more, from the viewpoint of obtaining a higher use effect. is preferred, and may be 25 parts by weight or more. In some aspects, the content of the terpene phenol resin with respect to 100 parts by weight of the acrylic polymer is suitably 80 parts by weight or less, preferably 60 parts by weight or less (for example, 55 parts by weight or less), more preferably 50 parts by weight or less, 45 parts by weight or less, 40 parts by weight or less, 35 parts by weight or less, 30 parts by weight or less, or 25 parts by weight or less. . Here, the fact that the content of the terpene phenol resin is X parts by weight or less with respect to 100 parts by weight of the acrylic polymer means that the adhesive layer does not contain the terpene phenol resin, and that the terpene phenol resin is added to the acrylic polymer. It is used in the sense of including both of containing at a ratio of X parts by weight or less with respect to 100 parts by weight. In some embodiments, the content of the terpene phenolic resin in the pressure-sensitive adhesive layer may be 10 parts by weight or less, 5 parts by weight or less, 3 parts by weight or less, or 1 part by weight with respect to 100 parts by weight of the acrylic polymer. parts or less (eg, 0 to 0.1 parts by weight).

When a phenolic tackifying resin is used as the tackifying resin, the content of the tackifying resin other than the phenolic tackifying resin (non-phenolic tackifying resin, such as a rosin-based tackifying resin) in the pressure-sensitive adhesive layer is For example, 40 parts by weight or less is suitable for 100 parts by weight of the polymer. As a result, the effect of including the phenolic tackifying resin can be favorably exhibited. In some embodiments, the amount of non-phenolic tackifying resin used is preferably about 20 parts by weight or less (e.g., less than 20 parts by weight), more preferably about 15 parts by weight or less, relative to 100 parts by weight of the acrylic polymer. and may be approximately 10 parts by weight or less, or may be approximately 5 parts by weight or less.

In some embodiments, a tackifying resin _TL having a softening point of less than 150° C. is used as the tackifying resin from the viewpoint of adhesion to the adherend. The lower limit of the softening point of the tackifying resin _TL is not particularly limited. In some embodiments, the softening point of the tackifier resin T _L is suitably about 60° C. or higher, for example, about 80° C. or higher, and about 90° C., from the viewpoint of exerting a suitable cohesive force. °C or higher, or about 100 °C or higher. As the tackifying resin _TL , one selected from those having a softening point of less than 150° C. among the tackifying resins exemplified above can be used singly or in combination of two or more.

In some embodiments, the tackifying resin T _L preferably comprises a phenolic tackifying resin. The tackifying resin _TL may contain one type of phenolic tackifying resin alone, or may contain two or more types of phenolic tackifying resin. The tackifying resin _TL may comprise a combination of phenolic and non-phenolic tackifying resins. As the non-phenol-based tackifying resin, one selected from among the above-exemplified tackifying resins other than the phenol-based tackifying resin and having a softening point of less than 150 ° C., alone or two or more. can be used in combination. In some embodiments, the proportion of the phenolic tackifying resin in the total tackifying resin T _L can be, for example, greater than about 50 wt%, can be greater than about 65 wt%, and can be greater than or equal to about 75 wt%. good too. The technology disclosed herein is an aspect in which substantially all of the tackifying resin T _L (for example, approximately 97% by weight or more, or 99% by weight or more, or even 100% by weight) is a phenolic tackifying resin. can be preferably implemented in

The content of the tackifier resin T _L (the total amount thereof when two or more tackifier resins T _L are included) is not particularly limited, but may be 80 parts by weight or less with respect to 100 parts by weight of the acrylic polymer. From the viewpoint of adhesion to the adherend, etc., it is preferably 60 parts by weight or less (for example, 55 parts by weight or less), more preferably 50 parts by weight or less, and may be 45 parts by weight or less, or 40 parts by weight. 35 parts by weight or less, 30 parts by weight or less, or 25 parts by weight or less. Further, the amount of the tackifying resin T _L used relative to 100 parts by weight of the acrylic polymer may be, for example, 5 parts by weight or more, 7 parts by weight or more, 9 parts by weight or more, 12 parts by weight or more, or 15 parts by weight. parts or more, or 18 parts by weight or more. In some embodiments, the amount of the tackifying resin T _L used relative to 100 parts by weight of the acrylic polymer is, for example, 18.5 parts by weight or more, and is 20 parts by weight or more, from the viewpoint of improving adhesive strength. is preferred, and may be 25 parts by weight or more.

In some embodiments, the adhesive layer may comprise a combination of a tackifying resin T _L and a tackifying resin T _H having a softening point of 150° C. or higher (eg, 150° C. to 200° C.). As the tackifying resin _TH , among the tackifying resins exemplified above, those having a softening point of 150° C. or higher can be used singly or in combination of two or more.

The softening point of the tackifier resin in this specification is defined as a value measured based on the softening point test method (ring and ball method) specified in JIS K5902 and JIS K2207. Specifically, the sample is melted as quickly as possible at the lowest possible temperature and carefully filled into a ring placed on a flat metal plate to avoid the formation of bubbles. After it cools down, cut off the raised part from the plane including the top of the ring with a slightly heated knife. Next, a supporter (ring base) is placed in a glass container (heating bath) having a diameter of 85 mm or more and a height of 127 mm or more, and glycerin is poured to a depth of 90 mm or more. Next, the steel ball (diameter 9.5 mm, weight 3.5 g) and the ring filled with the sample are immersed in the glycerin without touching each other, and the temperature of the glycerin is kept at 20° C.±5° C. for 15 minutes. . A steel ball is then centered on the surface of the sample in the ring and placed in position on the support. Next, the distance from the upper end of the ring to the glycerin surface is kept at 50 mm, a thermometer is placed, the center of the mercury ball of the thermometer is set at the same height as the center of the ring, and the container is heated. The Bunsen burner flame used for heating should be midway between the center and the rim of the bottom of the vessel to ensure even heating. The rate at which the bath temperature rises after reaching 40° C. after heating is started must be 5.0±0.5° C. per minute. The temperature at which the sample gradually softens and flows down the ring and finally touches the bottom plate is read and taken as the softening point. Two or more softening points are measured at the same time, and the average value is adopted.

In some embodiments, the tackifying resin T _L preferably accounts for more than 50% by weight of the total amount of tackifying resins contained in the adhesive layer. Thereby, the effect of containing the tackifying resin _TL is likely to be effectively exhibited. The ratio of the tackifying resin _TL to the total amount of the tackifying resin contained in the pressure-sensitive adhesive layer is preferably 60% by weight _or more, more preferably 60% by weight or more, more preferably 70% by weight or more, more preferably 80% by weight or more, particularly preferably 90% by weight or more, may be 95% by weight or more, or may be 98% by weight or more. In some preferred embodiments, the tackifying resin contained in the adhesive layer consists essentially of the tackifying resin _TL . In this embodiment, the ratio of the tackifier resin T _L to the total amount of tackifier resin contained in the adhesive layer is in the range of 99 to 100% by weight.

In some embodiments, the tackifying resin can include a tackifying resin having a hydroxyl value of 40 mgKOH/g or higher (eg, 40 mgKOH/g or higher, preferably 45 mgKOH/g or higher, more preferably 50 mgKOH/g or higher). Hereinafter, such a tackifying resin having a hydroxyl value is sometimes referred to as a "high hydroxyl value resin". Acrylic polymers containing n-HpA as a monomer unit have good compatibility with such high hydroxyl value resins. can increase In some embodiments, the high hydroxyl value resin may have a hydroxyl value of 60 mg KOH/g or greater, 80 mg KOH/g or greater, 90 mg KOH/g or greater, or 100 mg KOH/g or greater. The upper limit of the hydroxyl value of the high hydroxyl value resin is not particularly limited, and may be, for example, approximately 200 mgKOH/g or less, approximately 160 mgKOH/g or less, or approximately 140 mgKOH/g or less. In some aspects, from the viewpoint of adhesion to the adherend, the hydroxyl value of the high hydroxyl value resin is preferably about 125 mgKOH/g or less, may be about 115 mgKOH/g or less, or about 90 mgKOH/g or less. It's okay.

As the high hydroxyl value resin, one kind selected appropriately from those having a hydroxyl value corresponding to the high hydroxyl value resin among the tackifying resins exemplified above can be used alone or in combination of two or more kinds. In some embodiments, the high hydroxyl value resin preferably comprises a phenolic tackifying resin (eg, a terpene phenolic resin). The high hydroxyl value resin may contain one phenolic tackifying resin alone, or may contain two or more phenolic tackifying resins in combination. Further, the high hydroxyl value resin may be the tackifying resin T _L described above or the tackifying resin T _H. In some embodiments, a high hydroxyl value resin that is a tackifying resin _TL may be preferably employed. The high hydroxyl value resin, which is the tackifying resin _TL , can improve adhesiveness by containing more tackifying resin while suppressing deterioration in oil resistance and aqueous solvent resistance.

Although not particularly limited, the amount used when using a high hydroxyl value resin (for example, a high hydroxyl value resin having a hydroxyl value of more than 40 mgKOH/g, preferably 45 mgKOH/g or more, more preferably 50 mgKOH/g or more) (2 If more than one type of high hydroxyl value resin is included, the total amount thereof) can be, for example, 5 parts by weight or more with respect to 100 parts by weight of the acrylic polymer, and from the viewpoint of obtaining a higher effect, 10 parts by weight or more. (e.g., more than 10 parts by weight), more preferably 12 parts by weight or more, may be 15 parts by weight or more, may be 18 parts by weight or more (e.g., 18.5 parts by weight or more), or may be 20 parts by weight. or more, or 25 parts by weight or more. In addition, from the viewpoint of suppression of swelling degree and oil resistance, in some embodiments, the amount of the high hydroxyl value resin to be used with respect to 100 parts by weight of the acrylic polymer is appropriately 80 parts by weight or less, preferably 60 parts by weight. Parts by weight or less (for example, 55 parts by weight or less), more preferably 50 parts by weight or less, may be 45 parts by weight or less, may be 40 parts by weight or less, may be 35 parts by weight or less, may be 30 parts by weight or less, may be 25 parts by weight or less. It may be less than parts by weight.

In some embodiments, a high hydroxyl value resin (e.g., a high hydroxyl value resin with a hydroxyl value greater than 40 mg KOH/g, preferably 45 mg KOH/g or greater, more preferably 50 mg KOH/g or greater) is a tackifying It preferably accounts for more than 30% by weight of the total amount of resin, more preferably more than 50% by weight. As a result, the effect of increasing the adhesive strength while achieving both oil resistance and aqueous solvent resistance in a well-balanced manner can be preferably realized. In some aspects, the ratio of the high hydroxyl value resin to the total amount of the tackifying resin contained in the pressure-sensitive adhesive layer is preferably 60% by weight or more from the viewpoint of making it easier to exhibit the effect of using the high hydroxyl value resin. , more preferably 70% by weight or more, still more preferably 80% by weight or more, particularly preferably 90% by weight or more, and may be 95% by weight or more, or may be 98% by weight or more. In some preferred embodiments, the tackifier resin contained in the pressure-sensitive adhesive layer consists essentially of high hydroxyl value resin. In this embodiment, the ratio of the high hydroxyl value resin to the total amount of the tackifying resin contained in the pressure-sensitive adhesive layer is in the range of 99-100% by weight.

In some aspects, the tackifying resin can comprise a tackifying resin with a hydroxyl value of less than 40 mg KOH/g (eg, less than 30 mg KOH/g). Hereinafter, such a tackifying resin having a hydroxyl value is sometimes referred to as a "low hydroxyl value resin". The hydroxyl value of the low hydroxyl value resin may be about 20 mgKOH/g or less, may be about 15 mgKOH/g or less, or may be about 10 mgKOH/g or less. The lower limit of the hydroxyl value of the low hydroxyl value resin is not particularly limited, and may be substantially 0 mgKOH/g. A low hydroxyl value resin is preferably used in combination with a high hydroxyl value resin, and can be useful for adjusting adhesion properties and the like. Alternatively, the technology disclosed herein may be practiced using only low hydroxyl value resins as tackifying resins.

As the low hydroxyl value resin, one kind selected appropriately from those having a hydroxyl value corresponding to the low hydroxyl value resin among the tackifying resins exemplified above can be used alone or in combination of two or more kinds. In some embodiments, the low hydroxyl value resin preferably comprises a rosin-based tackifying resin. Examples The hydroxyl value resin may contain one type of rosin-based tackifying resin alone, or may contain two or more types of rosin-based tackifying resin in combination. Also, the low hydroxyl value resin may be the tackifying resin T _L described above or the tackifying resin T _H. In some embodiments, a low hydroxyl value resin that is a tackifying resin _TL may be preferably employed.

Although not particularly limited, the amount used in the case of using a low hydroxyl value resin (when two or more low hydroxyl value resins are included, the total amount thereof) is, for example, 1 per 100 parts by weight of the acrylic polymer. It may be at least 3 parts by weight, at least 5 parts by weight, at least 7 parts by weight, or at least 9 parts by weight. In addition, the amount of the low hydroxyl value resin to be used relative to 100 parts by weight of the acrylic polymer is usually suitably 50 parts by weight or less, may be 40 parts by weight or less, may be 30 parts by weight or less, or may be 20 parts by weight or less. 15 parts by weight or less, 10 parts by weight or less, 8 parts by weight or less, 4 parts by weight or less, or 2 parts by weight or less. A low hydroxyl value resin may not be used.

Here, as the value of the hydroxyl value, a value measured by a potentiometric titration method specified in JIS K0070:1992 can be adopted. A specific measuring method is as follows.
[Method for measuring hydroxyl value]
1. Reagent (1) As the acetylation reagent, approximately 12.5 g (approximately 11.8 mL) of acetic anhydride is taken, pyridine is added to bring the total amount to 50 mL, and the mixture is thoroughly stirred and used. Alternatively, take about 25 g (about 23.5 mL) of acetic anhydride, add pyridine to bring the total amount to 100 mL, and use the well-stirred solution.
(2) A 0.5 mol/L potassium hydroxide ethanol solution is used as a measurement reagent.
(3) In addition, prepare toluene, pyridine, ethanol and distilled water.
2. Operation (1) About 2 g of a sample is accurately weighed and collected in a flat-bottomed flask, 5 mL of an acetylation reagent and 10 mL of pyridine are added, and an air cooling tube is attached.
(2) After heating the flask in a bath at 100°C for 70 minutes, allowing it to cool, adding 35 mL of toluene as a solvent from the top of the cooling tube and stirring, then adding 1 mL of distilled water and stirring to obtain acetic anhydride. decompose. Heat again in the bath for 10 minutes for complete decomposition and allow to cool.
(3) Wash the cooling tube with 5 mL of ethanol and remove. Then, 50 mL of pyridine is added as a solvent and stirred.
(4) Add 25 mL of 0.5 mol/L potassium hydroxide ethanol solution using a whole pipette.
(5) Perform potentiometric titration with 0.5 mol/L potassium hydroxide ethanol solution. The inflection point of the obtained titration curve is taken as the end point.
(6) In the blank test, the above (1) to (5) are performed without any sample.
3. Calculation Calculate the hydroxyl value by the following formula.
Hydroxyl value (mgKOH/g) = [(BC) x f x 28.05]/S + D
here,
B: Amount (mL) of 0.5 mol/L potassium hydroxide ethanol solution used in the blank test,
C: Amount (mL) of 0.5 mol/L potassium hydroxide ethanol solution used for the sample,
f: factor of 0.5 mol/L potassium hydroxide ethanol solution,
S: weight of sample (g),
D: acid value,
28.05: ½ of the molecular weight of potassium hydroxide, 56.11;
is.

As the tackifying resin contained in the pressure-sensitive adhesive layer disclosed herein, a plant-derived tackifying resin (vegetable tackifying resin) can preferably act from the viewpoint of improving the biomass carbon ratio of the pressure-sensitive adhesive layer. Examples of vegetable tackifying resins include, for example, the above-described rosin-based tackifying resins and terpene-based tackifying resins. Vegetable tackifying resins can be used singly or in combination of two or more. The ratio of the vegetable tackifying resin to the total amount of the tackifying resin is preferably 30% by weight or more (for example, 50% by weight or more, typically 80% by weight or more). In some embodiments, the proportion of vegetable tackifying resin to the total amount of tackifying resin is 90% or more (eg, 95% or more, typically 99-100%) by weight. The technology disclosed herein can be preferably practiced in a mode substantially free of tackifying resins other than vegetable tackifying resins.

In the technology disclosed herein, the total content of the acrylic polymer and the tackifying resin in the pressure-sensitive adhesive layer is appropriately set so that the effect of the technology disclosed herein is exhibited, and is limited to a specific range. not something. The total amount (total amount) of the acrylic polymer and the tackifying resin contained in the pressure-sensitive adhesive layer according to some preferred embodiments is more than 50% by weight from the viewpoint of preferably exhibiting the effects of the technology disclosed herein. is suitable, preferably about 70% by weight or more, more preferably about 90% by weight or more, still more preferably 95% by weight or more (for example, 95% by weight or more and 100% by weight or less or less than 100% by weight), and 97% by weight % or more.

(crosslinking agent)
In the technique disclosed here, the adhesive composition used for forming the adhesive layer may contain a cross-linking agent as needed. The type of cross-linking agent is not particularly limited. Alkoxide cross-linking agents, metal chelate cross-linking agents, metal salt cross-linking agents, carbodiimide cross-linking agents, hydrazine cross-linking agents, amine cross-linking agents, silane coupling agents and the like can be mentioned. A crosslinking agent can be used individually by 1 type or in combination of 2 or more types. Among them, preferred are epoxy-based cross-linking agents, isocyanate-based cross-linking agents, oxazoline-based cross-linking agents, aziridine-based cross-linking agents, and melamine-based cross-linking agents, and more preferred are epoxy-based cross-linking agents and isocyanate-based cross-linking agents. By appropriately selecting and using a cross-linking agent, a cohesion degree of 100 or less can be preferably achieved. The pressure-sensitive adhesive layer in the technology disclosed herein contains the cross-linking agent in the form after the cross-linking reaction, the form before the cross-linking reaction, the form after the cross-linking reaction, the intermediate or composite form thereof, and the like. can contain The cross-linking agent is typically contained in the pressure-sensitive adhesive layer exclusively in the form after the cross-linking reaction.

As the epoxy-based cross-linking agent, a compound having two or more epoxy groups in one molecule can be used without particular limitation. An epoxy-based cross-linking agent having 3 to 5 epoxy groups in one molecule is preferred. Epoxy-based cross-linking agents may be used singly or in combination of two or more.

Specific examples of epoxy-based cross-linking agents include, but are not limited to, N,N,N',N'-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N-diglycidylaminomethyl ) cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether and the like. Commercial products of epoxy-based cross-linking agents include Mitsubishi Gas Chemical Company's trade name "TETRAD-C" and trade name "TETRAD-X", DIC's trade name "Epiclon CR-5L", and Nagase ChemteX Corporation. and "TEPIC-G" manufactured by Nissan Chemical Industries, Ltd. under the trade name of "Denacol EX-512".

The amount of the epoxy-based cross-linking agent used is not particularly limited. The amount of the epoxy-based cross-linking agent used is, for example, more than 0 parts by weight and about 1 part by weight or less (typically about 0.001 to 1 part by weight) with respect to 100 parts by weight of the acrylic polymer. can. From the viewpoint of suitably exhibiting the effect of improving the cohesive strength, the amount of the epoxy-based cross-linking agent to be used is appropriately about 0.005 parts by weight or more, and about 0.01 part by weight, relative to 100 parts by weight of the acrylic polymer. Parts by weight or more (e.g., greater than 0.01 parts by weight, or 0.015 parts by weight or more) are preferred, and about 0.02 parts by weight or more (e.g., greater than 0.02 parts by weight, or 0.025 parts by weight or more) are more preferred. In addition, from the viewpoint of improving the adhesion to the adherend, the amount of the epoxy-based cross-linking agent to be used is appropriately about 0.5 parts by weight or less, and about 0.2 parts by weight, per 100 parts by weight of the acrylic polymer. It is preferably not more than 0.1 part by weight, more preferably not more than 0.1 part by weight (for example, less than 0.1 part by weight), may be not more than 0.07 part by weight, or may be not more than 0.05 part by weight. It may be 0.04 parts by weight or less (for example, less than 0.04 parts by weight), may be less than 0.035 parts by weight, or may be 0.03 parts by weight or less.

As the isocyanate-based cross-linking agent, polyfunctional isocyanates (compounds having an average of two or more isocyanate groups per molecule, including those having an isocyanurate structure) can be preferably used. The isocyanate-based cross-linking agents may be used singly or in combination of two or more.

Examples of polyfunctional isocyanates include aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates.
Specific examples of aliphatic polyisocyanates include 1,2-ethylene diisocyanate; tetramethylene diisocyanates such as 1,2-tetramethylene diisocyanate, 1,3-tetramethylene diisocyanate, and 1,4-tetramethylene diisocyanate; - hexamethylene diisocyanates such as hexamethylene diisocyanate, 1,3-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5-hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,5-hexamethylene diisocyanate; 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, lysine diisocyanate, and the like.

Specific examples of alicyclic polyisocyanates include isophorone diisocyanate; cyclohexyl diisocyanates such as 1,2-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate and 1,4-cyclohexyl diisocyanate; 1,2-cyclopentyl diisocyanate, 1,3 - cyclopentyl diisocyanate such as cyclopentyl diisocyanate; hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and the like.

Specific examples of aromatic polyisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, and 2,2'-diphenylmethane diisocyanate. , 4,4′-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4′-diisocyanate, 2,2′-diphenylpropane-4,4′-diisocyanate, 3,3′-dimethyldiphenylmethane-4,4′-diisocyanate , 4,4′-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3′-dimethoxydiphenyl-4,4′-diisocyanate , xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate, and the like.

Examples of preferred polyfunctional isocyanates include polyfunctional isocyanates having an average of 3 or more isocyanate groups per molecule. Such tri- or more functional isocyanates are polymers (typically dimers or trimers) of di- or tri- or more functional isocyanates, derivatives (for example, polyhydric alcohols and two or more molecules of polyfunctional isocyanates). addition reaction products), polymers, and the like. For example, dimers and trimers of diphenylmethane diisocyanate, isocyanurate of hexamethylene diisocyanate (trimeric adduct of isocyanurate structure), reaction products of trimethylolpropane and tolylene diisocyanate, trimethylolpropane and hexa Polyfunctional isocyanates such as reaction products with methylene diisocyanate, polymethylene polyphenyl isocyanate, polyether polyisocyanate, polyester polyisocyanate, and the like can be mentioned. Commercially available polyfunctional isocyanates include "Duranate TPA-100" (trade name) manufactured by Asahi Kasei Chemicals, "Coronate L" (trade name), "Coronate HL", "Coronate HK" (trade name) and "Coronate HK" (trade names) manufactured by Tosoh Corporation. HX", "Coronate 2096", and the like.

The amount of the isocyanate-based cross-linking agent to be used is not particularly limited, and can be, for example, approximately 0.1 parts by weight or more with respect to 100 parts by weight of the acrylic polymer. From the viewpoint of coexistence of adhesive strength, oil resistance and aqueous solvent resistance, etc., the amount of the isocyanate cross-linking agent used relative to 100 parts by weight of the acrylic polymer can be, for example, 0.5 parts by weight or more, and 1.0 parts by weight. 1.5 parts by weight or more is advantageous, preferably 2.0 parts by weight or more, more preferably 2.5 parts by weight or more, and 2.8 parts by weight or more. 3.0 parts by weight or more, or 3.5 parts by weight or more. In addition, the amount of the isocyanate-based cross-linking agent used is suitably 10 parts by weight or less, preferably less than 8.0 parts by weight, more preferably less than 7.0 parts by weight, per 100 parts by weight of the acrylic. , more preferably less than 6.0 parts by weight, and may be less than 5.0 parts by weight or less than 4.5 parts by weight.

In some preferred embodiments, as the cross-linking agent, an epoxy-based cross-linking agent and at least one cross-linking agent having a different type of cross-linkable functional group from the epoxy-based cross-linking agent are used in combination. According to the technique disclosed herein, a cross-linking agent other than an epoxy-based cross-linking agent (that is, a cross-linking agent having a different type of cross-linkable reactive group from the epoxy-based cross-linking agent; hereinafter also referred to as a "non-epoxy cross-linking agent"). By using it in combination with an epoxy-based cross-linking agent, it is possible to favorably achieve both adhesion to different materials and high holding power.

The type of non-epoxy cross-linking agent that can be used in combination with the epoxy cross-linking agent is not particularly limited, and can be appropriately selected from the cross-linking agents described above. Non-epoxy crosslinking agents may be used singly or in combination of two or more.

In some preferred embodiments, an isocyanate cross-linking agent can be employed as the non-epoxy cross-linking agent. For example, by using an epoxy-based cross-linking agent and an isocyanate-based cross-linking agent in combination, more excellent adhesive properties can be achieved. The relationship between the content of the epoxy-based cross-linking agent and the content of the non-epoxy-based cross-linking agent (preferably isocyanate-based cross-linking agent) is not particularly limited. The content of the epoxy-based cross-linking agent can be, for example, about 1/10 or less of the content of the non-epoxy-based cross-linking agent (preferably isocyanate-based cross-linking agent). From the viewpoint of achieving both adhesion to the adherend and cohesive strength, it is appropriate that the content of the epoxy-based cross-linking agent is about 1/30 or less of the content of the non-epoxy-based cross-linking agent. It is preferably about 1/50 or less (for example, about 1/60 or less), more preferably about 1/75 or less, and may be about 1/90 or less. In addition, from the viewpoint of suitably exhibiting the effect of using a combination of an epoxy-based cross-linking agent and a non-epoxy cross-linking agent (preferably an isocyanate-based cross-linking agent), the content of the epoxy-based cross-linking agent is usually about 1/1000 or more, for example about 1/500 or more, preferably about 1/300 or more, more preferably 1/180 or more (e.g. 1/150 or more) of the content of the system crosslinking agent, More preferably, it is 1/120 or more.

The total amount of the cross-linking agent used is not particularly limited, and for example, about 0.005 parts by weight or more (for example, 0.01 parts by weight or more, typically 0.1 parts by weight or more) with respect to 100 parts by weight of the acrylic polymer. about 10 parts by weight or less (for example, about 8 parts by weight or less, preferably about 5 parts by weight or less).

(Other additives)
In addition to the components described above, the pressure-sensitive adhesive composition may optionally contain a leveling agent, a cross-linking aid, a plasticizer, a softening agent, a filler, a coloring agent (pigment, dye, etc.), an antistatic agent, and an anti-aging agent. , ultraviolet absorbers, antioxidants, light stabilizers, and other additives commonly used in the field of adhesives. As for such various additives, conventionally known ones can be used in a conventional manner, and since they do not particularly characterize the present invention, detailed description thereof will be omitted.

(degree of swelling)
The pressure-sensitive adhesive layer in the technology disclosed herein has a swelling degree of 100 or less with respect to ethyl acetate. By using an acrylic polymer containing n-HpA as a monomer component and setting the content of the tackifying resin to more than 10 parts by weight with respect to 100 parts by weight of the acrylic polymer under the condition that the degree of swelling is 100 or less, the adhesive strength is improved. can be effectively increased, and a decrease in adhesive strength due to contact with oil or aqueous solvent can be suppressed. As a result, it is possible to realize a PSA sheet that achieves a high level of adhesive strength, oil resistance, and aqueous solvent resistance. In some aspects, the degree of swelling of the pressure-sensitive adhesive layer is preferably 90 or less, more preferably 80 or less, may be 75 or less, may be 70 or less, or may be 65 or less, from the viewpoint of improving oil resistance. 60 or less (for example, less than 60). The lower limit of the degree of swelling is not particularly limited, and may be 10 or more, for example. From the viewpoint of adhesion to the adherend, in some embodiments, the degree of swelling of the pressure-sensitive adhesive layer is suitably 30 or more, preferably 35 or more, more preferably 40 or more. Preferably, it may be 45 or more (eg, greater than 45), or 50 or more. By appropriately adjusting the swelling degree of the pressure-sensitive adhesive layer within the above range, the swelling degree of the pressure-sensitive adhesive layer is measured by the method described in Examples below. The degree of swelling can be adjusted by adjusting the monomer composition of the acrylic polymer, the Mw, the adhesive composition such as the tackifying resin and the cross-linking agent.

(Formation of adhesive layer)
The pressure-sensitive adhesive layer (layer comprising pressure-sensitive adhesive) disclosed herein is formed from a water-based pressure-sensitive adhesive composition, a solvent-based pressure-sensitive adhesive composition, a hot-melt pressure-sensitive adhesive composition, or an active energy ray-curable pressure-sensitive adhesive composition. It can be a pressure-sensitive adhesive layer. The water-based pressure-sensitive adhesive composition refers to a pressure-sensitive adhesive composition in the form of containing a pressure-sensitive adhesive (adhesive layer-forming component) in a water-based solvent (aqueous solvent), typically water-dispersed. Also included are so-called type adhesive compositions (compositions in which at least part of the adhesive is dispersed in water) and the like. Moreover, the solvent-type adhesive composition refers to an adhesive composition in the form of containing an adhesive in an organic solvent. As the organic solvent contained in the solvent-based pressure-sensitive adhesive composition, one or two or more of the organic solvents (toluene, ethyl acetate, etc.) exemplified as the organic solvent (toluene, ethyl acetate, etc.) that can be used in the above solution polymerization can be used without particular limitation. The technology disclosed herein can be preferably implemented in a mode comprising a pressure-sensitive adhesive layer formed from a solvent-based pressure-sensitive adhesive composition, from the viewpoint of adhesive properties and the like.

The adhesive layer disclosed here can be formed by a conventionally known method. For example, a method of forming a pressure-sensitive adhesive layer by applying a pressure-sensitive adhesive composition to a releasable surface (release surface) or a non-releasable surface and drying can be employed. In a pressure-sensitive adhesive sheet having a substrate, for example, a method (direct method) of forming a pressure-sensitive adhesive layer by directly applying (typically applying) a pressure-sensitive adhesive composition to the substrate and drying it is adopted. be able to. Alternatively, a method of applying a pressure-sensitive adhesive composition to a surface having releasability (release surface) and drying to form a pressure-sensitive adhesive layer on the surface and transferring the pressure-sensitive adhesive layer to a substrate (transfer method). may be adopted. From the viewpoint of productivity, the transfer method is preferred. As the release surface, the surface of a release liner, the back surface of a base material subjected to a release treatment, or the like can be used. The pressure-sensitive adhesive layer disclosed herein is typically formed continuously, but is not limited to such a form. It may be a formed pressure-sensitive adhesive layer.

Application of the pressure-sensitive adhesive composition can be performed using a conventionally known coater such as a gravure roll coater, die coater, bar coater, and the like. Alternatively, the adhesive composition may be applied by impregnation, curtain coating, or the like.
From the viewpoint of promoting the cross-linking reaction, improving production efficiency, etc., it is preferable to dry the pressure-sensitive adhesive composition under heating. The drying temperature can be, for example, about 40 to 150°C, preferably about 60 to 130°C. After drying the pressure-sensitive adhesive composition, it may be further aged for the purpose of adjusting migration of components in the pressure-sensitive adhesive layer, progressing the crosslinking reaction, relaxing strain that may exist in the pressure-sensitive adhesive layer, and the like.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, and a structure having a pressure-sensitive adhesive layer having an appropriate thickness in the range of, for example, 0.1 μm to 500 μm can be employed depending on the application, purpose of use, and the like. In some embodiments, the thickness of the adhesive layer is suitably about 100 μm or less, preferably about 70 μm or less, more preferably about 50 μm or less, from the viewpoint of avoiding the adhesive sheet from becoming excessively thick. , and more preferably about 35 μm or less. In the pressure-sensitive adhesive sheet according to some preferred embodiments, the thickness of the pressure-sensitive adhesive layer may be approximately 30 μm or less (eg, less than 30 μm), approximately 25 μm or less (eg, less than 25 μm), or approximately 22 μm or less, It may be approximately 20 μm or less (for example, less than 20 μm). A pressure-sensitive adhesive layer with a limited thickness can well meet demands for thinning and weight reduction. In general, when the thickness of the pressure-sensitive adhesive layer becomes smaller, the adhesive force tends to decrease, and the adhesion to the adherend tends to decrease, which tends to facilitate the penetration of oil and aqueous solvents into the interface. According to the technology disclosed herein, it is possible to realize a pressure-sensitive adhesive sheet having a structure having a pressure-sensitive adhesive layer with a limited thickness and having high levels of adhesive strength, oil resistance, and aqueous solvent resistance. . From the viewpoint of adhesion to the adherend, the lower limit of the thickness of the pressure-sensitive adhesive layer is appropriately about 0.5 μm or more in some embodiments, may be about 1 μm or more, or about 3 μm or more. is preferably about 7 μm or greater, more preferably about 10 μm or greater, even more preferably about 12 μm or greater (eg, greater than 12 μm), may be about 15 μm or greater, or may be about 18 μm or greater. The greater the thickness of the pressure-sensitive adhesive layer, the easier it is to achieve the target adhesive strength. In some embodiments, the thickness of the adhesive layer may be greater than 20 μm, or greater than or equal to 24 μm, or greater than or equal to 27 μm.

The pressure-sensitive adhesive sheet disclosed herein may be a pressure-sensitive adhesive sheet having pressure-sensitive adhesive layers having the thicknesses described above on both sides of a substrate. Further, in a double-sided pressure-sensitive adhesive sheet with a substrate having a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer on each side of the substrate, the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer have the same thickness. There may be one, or they may have mutually different thicknesses.

(Surface free energy γ)
In some aspects, the surface free energy γ of the adhesive layer is preferably less than 40 mJ/m ² . The surface free energy γ of the pressure-sensitive adhesive layer is a value represented by the following formula: γ=γ ^d +γ ^p +γ ^h . Here, γ ^d , γ ^p and γ ^h in the above formula represent the dispersion component, polar component and hydrogen bond component of the surface free energy, respectively. The surface free energy γ of the pressure-sensitive adhesive layer was determined using water, diiodomethane, and 1-bromonaphthalene as probe liquids, and from the contact angle of each probe liquid, the Kitazaki-Hata formula (Journal of the Adhesion Society of Japan, Vol.8, No.3, 1972 , pp.131-141). A contact angle can be measured using a commercially available contact angle meter. As the contact angle meter, the product name "CA-X" manufactured by Kyowa Interface Science Co., Ltd. can be used. A droplet method is used for the measurement, and the contact angle is measured from the droplet shape after 1500 ms of droplet deposition. A similar method is adopted in the examples described later.

When the surface free energy γ of the pressure-sensitive adhesive layer decreases, the wettability of the pressure-sensitive adhesive layer to the adherend tends to improve, and the adhesion of the interface (bonding interface) between the pressure-sensitive adhesive layer and the adherend tends to increase. . By increasing the adhesiveness of the adhesive interface in this way, it is possible to suppress the penetration of oil and aqueous solvents from the outer edge of the pressure-sensitive adhesive sheet into the adhesive interface. Therefore, it is preferable to increase the adhesion at the interface between the pressure-sensitive adhesive layer and the adherend from the viewpoint of suppressing the decrease in adhesive force due to contact with oil or aqueous solvent. It is preferable to increase the adhesion at the interface between the pressure-sensitive adhesive layer and the adherend from the viewpoint of suppressing the decrease in the adhesive force due to contact with oil or aqueous solvent.

From the viewpoint of making it easier to obtain higher adhesion, in some embodiments, the surface free energy γ of the pressure-sensitive adhesive layer is preferably about 35 mJ/m ² or less, more preferably about 30 mJ/m ² or less, and is 27 mJ/m. m ² or less, 25 mJ/m ² or less, or 20 mJ/m ² or less. Although the lower limit of the surface free energy γ of the pressure-sensitive adhesive layer is not particularly limited, it is usually about 7 mJ/m ² or more, preferably about 10 mJ/m ² or more. In some aspects, the surface free energy γ of the pressure-sensitive adhesive layer may be 15 mJ/m ² or more, or 20 mJ/m ² or more. The surface free energy γ of the pressure-sensitive adhesive layer can be adjusted by, for example, the composition of the monomer components constituting the acrylic polymer, the type and amount of the tackifier resin used, and the like.

(Gel fraction)
The gel fraction of the pressure-sensitive adhesive layer disclosed herein is not particularly limited, and may be, for example, within the range of 20% to 80% (by weight). By increasing the gel fraction of the pressure-sensitive adhesive layer within an appropriate range, cohesiveness can be imparted to the pressure-sensitive adhesive layer, and reduction in adhesive force due to contact with oil or aqueous solvent can be suppressed. In some embodiments, the gel fraction of the adhesive layer is suitably greater than 30%, advantageously greater than 40%, may be greater than 45%, may be greater than 50%, may be greater than 55%, % or more, 60% or more, for example, more than 63%. Further, from the viewpoint of adhesion to the adherend, in some embodiments, the gel fraction of the pressure-sensitive adhesive layer is preferably 75% or less, and preferably 70% or less (for example, less than 70%). It is more preferably 68% or less, or even 66% by weight or less.

The gel fraction is measured by the following method. That is, about 0.1 g of adhesive sample (weight Wg ₁ ) was wrapped with a porous polytetrafluoroethylene membrane (weight Wg ₂ ) having an average pore size of 0.2 μm in a purse-like shape, and the opening was closed with a string (weight Wg ₃ ). tie up As the porous polytetrafluoroethylene (PTFE) membrane, trade name "Nitoflon (registered trademark) NTF1122" available from Nitto Denko Corporation (average pore size 0.2 μm, porosity 75%, thickness 85 μm) or equivalent use the product. The package was immersed in 50 mL of ethyl acetate and kept at room temperature (about 23°C) for 7 days, then the package was taken out, the ethyl acetate adhering to the outer surface was wiped off, and the package was dried at 130°C for 2 hours. Measure the weight of the packet (Wg ₄ ). The gel fraction of the pressure-sensitive adhesive layer is obtained by substituting each value into the following formula.
Gel fraction (%) = [( _Wg4 - _Wg2 - _Wg3 )/ _Wg1 ] x 100

(biomass carbon ratio)
In some embodiments, the pressure-sensitive adhesive layer may contain a biomass-derived material and have a biomass-carbon ratio equal to or greater than a predetermined value. The biomass carbon ratio of the adhesive layer is, for example, 1% or more, may be 10% or more, preferably 30% or more, and more preferably 50% or more. A high biomass carbon ratio of the adhesive means that the amount of fossil resource-based materials such as petroleum used is small. From this point of view, the higher the biomass carbon ratio of the adhesive, the better. For example, the biomass carbon ratio of the adhesive layer may be 55% or more, 60% or more, 70% or more, 75% or more, 80% or more, or more than 80%. good. The upper limit of the biomass carbon ratio is 100% by definition, and may be 99% or less. From the viewpoint of availability of materials, it may be 95% or less or 90% or less. From the viewpoint of facilitating good adhesion performance, in some embodiments, the biomass carbon ratio of the adhesive layer may be, for example, 90% or less, 85% or less, or 80% or less.

<Base material>
In the embodiment in which the pressure-sensitive adhesive sheet disclosed herein is in the form of a single-sided pressure-sensitive adhesive type or double-sided pressure-sensitive adhesive type pressure-sensitive adhesive sheet with a substrate, the substrate that supports (backs) the pressure-sensitive adhesive layer may be resin film, paper, cloth, or rubber. Sheets, foam sheets, metal foils, composites thereof, and the like can be used. Examples of resin films include polyolefin films such as polyethylene (PE), polypropylene (PP), and ethylene/propylene copolymer; polyester films such as polyethylene terephthalate (PET); vinyl chloride resin films; vinyl acetate resin films; resin film; polyamide resin film; fluorine resin film; cellophane and the like. Examples of paper include Japanese paper, kraft paper, glassine paper, woodfree paper, synthetic paper, top coat paper, and the like. Examples of fabrics include woven fabrics and non-woven fabrics obtained by spinning various fibrous materials alone or by blending them. Examples of the fibrous substance include cotton, staple fiber, Manila hemp, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, polyolefin fiber, and the like. Examples of rubber sheets include natural rubber sheets and butyl rubber sheets. Examples of foam sheets include foamed polyolefin sheets, foamed polyurethane sheets, foamed polychloroprene rubber sheets, and the like. Examples of metal foil include aluminum foil and copper foil. The substrate supporting the adhesive layer is also referred to as a substrate layer in the adhesive sheet.

The substrate may be formed from a biomass-derived material or may be formed from a non-biomass-derived material. A biomass-derived base material (typically a resin film) is preferably used from the viewpoint of pressure-sensitive adhesive sheet production that takes into account the suppression of dependence on fossil resource-based materials.

Also, the base material may be formed using a recyclable material or a recycled material (also referred to as a recycled material). A resin film is preferably used as such a recycled material. Since resin films (e.g., polyester films such as PET films) can be recycled, sustainable reproduction can be achieved by reusing used resin films regardless of whether plant-derived materials are used or not. is possible, and the environmental load can be reduced. Such recyclable resin films and recycled resin films are also called recycled films. The recycled material (for example, recycled film) may be formed from a biomass-derived material, or may be formed from a non-biomass-derived material.

As the base material constituting the pressure-sensitive adhesive sheet with a base material, a base film containing a resin film can be preferably used. The base film is typically an independently shape-maintainable (independent) member. The substrate in the technology disclosed herein can be substantially composed of such a base film. Alternatively, the substrate may contain an auxiliary layer in addition to the base film. Examples of the auxiliary layer include a colored layer, a reflective layer, an undercoat layer, an antistatic layer, etc. provided on the surface of the base film.

The resin film is a film containing a resin material as a main component (for example, a component contained in the resin film in an amount exceeding 50% by weight). Examples of resin films include polyolefin resin films such as polyethylene (PE), polypropylene (PP), and ethylene/propylene copolymer; polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), and the like. vinyl chloride resin film; vinyl acetate resin film; polyimide resin film; polyamide resin film; fluorine resin film; The resin film may be a rubber-based film such as a natural rubber film or a butyl rubber film. Among them, from the viewpoint of handleability and workability, polyester films are preferable, and among them, PET films are particularly preferable.

In this specification, the term "resin film" is typically a non-porous sheet, and is a concept distinguished from so-called nonwoven fabrics and woven fabrics (in other words, a concept excluding nonwoven fabrics and woven fabrics). be. The resin film may be a non-stretched film, a uniaxially stretched film, or a biaxially stretched film. Also, such resin films may be non-foamed. Here, the non-foamed resin film refers to a resin film that has not been intentionally treated to form a foam. Specifically, the non-foamed resin film may be a resin film having an expansion ratio of less than 1.1 times (for example, less than 1.05 times, typically less than 1.01 times).

If necessary, the base material (for example, resin film) may contain fillers (inorganic fillers, organic fillers, etc.), colorants, dispersants (surfactants, etc.), anti-aging agents, antioxidants, ultraviolet Various additives such as absorbents, antistatic agents, lubricants and plasticizers may be added. The blending ratio of various additives is about less than 30% by weight (for example, less than 20% by weight, typically less than 10% by weight).

The base material (for example, resin film) may have a single-layer structure, or may have a multi-layer structure of two layers, three layers, or more. From the viewpoint of shape stability, the substrate preferably has a single-layer structure. In the case of a multilayer structure, at least one layer (preferably all layers) is preferably a layer having a continuous structure of the resin (for example, polyester resin). A method for manufacturing the substrate (typically a resin film) is not particularly limited, and a conventionally known method may be appropriately adopted. For example, conventionally known general film forming methods such as extrusion molding, inflation molding, T-die casting, and calender roll molding can be employed as appropriate.

The surface of the substrate may be subjected to conventionally known surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, application of a primer, and the like. Such a surface treatment can be a treatment for improving the adhesion between the substrate and the adhesive layer, in other words, the anchoring property of the adhesive layer to the substrate.

Moreover, when the technology disclosed herein is implemented in the form of a single-sided pressure-sensitive adhesive sheet with a substrate, the back surface of the substrate may be subjected to release treatment as necessary. For the release treatment, for example, general silicone-based, long-chain alkyl-based, and fluorine-based release agents are typically applied to a thin film of about 0.01 μm to 1 μm (eg, 0.01 μm to 0.1 μm). It can be a treatment to give. By performing such a peeling treatment, it is possible to obtain effects such as facilitating the unwinding of the adhesive sheet wound into a roll.

In the pressure-sensitive adhesive sheet containing a substrate, the thickness of the substrate is not particularly limited. From the viewpoint of avoiding excessive thickness of the pressure-sensitive adhesive sheet, the thickness of the substrate can be, for example, approximately 200 μm or less, preferably approximately 150 μm or less, and more preferably approximately 100 μm or less. The thickness of the base material may be approximately 70 μm or less, approximately 50 μm or less, or approximately 30 μm or less (for example, approximately 25 μm or less) depending on the intended use and usage mode of the pressure-sensitive adhesive sheet. In some embodiments, the thickness of the base film layer may be about 20 μm or less, about 15 μm or less, about 10 μm or less (eg, about 5 μm or less). By reducing the thickness of the substrate, the thickness of the adhesive layer can be increased even if the total thickness of the adhesive sheet is the same. Increasing the thickness of the pressure-sensitive adhesive layer can be advantageous from the viewpoint of improving adhesion to adherends and substrates. The lower limit of the base material is not particularly limited. From the standpoint of handleability and workability of the pressure-sensitive adhesive sheet, the thickness of the base material is suitably about 0.5 μm or more (for example, 1 μm or more), preferably about 2 μm or more, for example, about 2 μm or more. It is 6 μm or more, may be approximately 8 μm or more, or may be approximately 10 μm or more. In some embodiments, the thickness of the substrate may be approximately 15 μm or greater, or approximately 25 μm or greater.

<Release liner>
In the technology disclosed herein, a release liner can be used in the formation of the adhesive layer, production of the adhesive sheet, storage of the adhesive sheet before use, distribution, shape processing, and the like. The release liner is not particularly limited, and for example, a release liner having a release treatment layer on the surface of a liner substrate such as a resin film or paper, a release liner made of a fluoropolymer (such as polytetrafluoroethylene), or the like is used. be able to. The release treatment layer may be formed by surface-treating the liner base material with a release treatment agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide release agent. As the liner base material, a material formed using a biomass-derived material or a recycled material (recycled film, etc.) can be preferably used, similarly to the base material of the pressure-sensitive adhesive sheet described above.

<Total thickness of adhesive sheet>
The total thickness of the adhesive sheet disclosed herein (including an adhesive layer and may further include a base layer, but not including a release liner) is not particularly limited. The total thickness of the adhesive sheet is, for example, approximately 1 mm or less, may be approximately 500 μm or less, or approximately 300 μm or less, and from the viewpoint of thinning, approximately 200 μm or less is appropriate, and approximately 150 μm or less. (for example, about 100 μm or less). In some preferred embodiments, the thickness of the adhesive sheet can be approximately 70 μm or less, such as approximately 55 μm or less. The lower limit of the thickness of the pressure-sensitive adhesive sheet is, for example, 0.1 μm or more (for example, 0.5 μm or more), suitably about 3 μm or more, preferably about 10 μm or more, more preferably about 15 μm or more, It may be about 20 μm or more, or about 40 μm or more. A pressure-sensitive adhesive sheet having a thickness of a predetermined value or more tends to have good adhesion to an adherend and also tends to be excellent in handleability. In addition, in the substrate-less adhesive sheet, the thickness of the adhesive layer is the total thickness of the adhesive sheet.

<Characteristics of adhesive sheet>
(Adhesive strength to SUS (initial adhesive strength F ₀ ))
In some aspects of the pressure-sensitive adhesive sheet disclosed herein, the pressure-sensitive adhesive sheet preferably has a 180-degree peel strength (adhesive strength to SUS) of 8.0 N/10 mm or more to a stainless steel plate. A pressure-sensitive adhesive sheet exhibiting such adhesive strength to SUS can exhibit good fixing performance, for example, in applications for fixing members. The adhesive strength to SUS is more preferably about 8.2 N/10 mm or more, more preferably 8.5 N/10 mm or more, and may be 8.8 N/10 mm or more, or 9.0 N/10 mm or more. It may be 2 N/10 mm or more, 9.5 N/10 mm or more, or 9.7 N/10 mm or more. Higher adhesion to SUS can be advantageous in fixing small or narrow members, and in fixing members whose joints may be subject to a relatively large load due to their own weight or external force. The upper limit of the adhesive strength to SUS is not particularly limited, but it may be, for example, 20 N/10 mm or less, 18 N/10 mm or less, or 16 N in consideration of other requirements (for example, thinning of the adhesive layer). /10 mm or less. The adhesion to SUS is measured using a SUS plate as an adherend under the conditions of a tensile speed of 300 mm/min and a peeling angle of 180 degrees in a measurement environment of 23° C. and 50% RH. The adhesive strength to SUS is a property measured without supplying oil or aqueous solvent after application to an adherend. In order to indicate the relationship between post-immersion adhesive strengths F _A and F _B to be described later, the adhesive strength to SUS may be referred to as “initial adhesive strength F ₀ ” below. More specifically, the initial adhesive force _F0 is measured by the method described in Examples below.

(Adhesive strength retention rate R _A )
In some embodiments of the adhesive sheet disclosed herein, the adhesive sheet has the following formula:
Adhesive force retention rate _RA [%] = (adhesive force after immersion F _A / initial adhesive force F ₀ ) × 100;
The adhesive strength retention rate _RA represented by is preferably 60% or more. Here, the adhesive force after immersion F _A in the above formula is measured after attaching the adhesive sheet to be evaluated to a stainless steel plate and immersing it in oleic acid for 2 weeks in an environment of 40 ° C. and 90% RH. It is the peel strength, and the initial adhesive force _F0 in the above formula is the above-mentioned adhesive force to SUS. More specifically, the post-immersion adhesive force _FA is measured by the method described in Examples below. The adhesive force retention rate _RA is calculated from the post-immersion adhesive force F _A and the initial adhesive force _F0 according to the above formula.

From the viewpoint of better suppressing the decrease in adhesive strength due to contact with oil, in some embodiments, the adhesive strength retention rate _RA is more preferably 63% or more (for example, 65% or more), and 67%. It is more preferably 73% or more, 75% or more, 80% or more, or 85% or more. The upper limit of the adhesive strength retention rate _RA is not particularly limited. The adhesive strength retention rate _RA is typically 100% or less, and from the viewpoint of compatibility with other properties (e.g., initial adhesive strength F ₀ and aqueous solvent resistance), in some embodiments, for example It may be 98% or less, 95% or less, 90% or less, 85% or less, or 80% or less. Further, in some aspects, from the viewpoint of bonding reliability against contact with oil, the post-immersion adhesive force _FA is preferably 4.8 N/10 mm or more (e.g., 5.0 N/10 mm or more), It is more preferably 5.3 N/10 mm or more (for example, 5.5 N/10 mm), more preferably 6.0 N/10 mm or more, and may be 6.5 N/10 mm or more, or 7.0 N/ It may be 10 mm or more, or 7.5 N/10 mm or more. The upper limit of the post-immersion adhesive force _FA is not particularly limited. In some embodiments, from the viewpoint of compatibility with other properties (eg, initial adhesive strength F ₀ and aqueous solvent resistance), the post-immersion adhesive strength F _A may be, for example, 19 N/10 mm or less, 17 N /10 mm or less, or 15 N/10 mm or less.

(Adhesive strength maintenance rate R _B )
In some embodiments of the adhesive sheet disclosed herein, the adhesive sheet has the following formula:
Adhesive strength maintenance rate R _B [%] = (post-immersion adhesive strength F _B / initial adhesive strength F ₀ ) × 100;
It is preferable that the adhesive force retention rate _RB represented by is 70% or more. Here, the adhesive strength after immersion F _B in the above formula is obtained by attaching the adhesive sheet to be evaluated to a stainless steel plate and placing it in an environment of 40 ° C. and 90% RH in a 50% isopropyl alcohol aqueous solution (volume ratio of 1:1). Solvent) is the 180 degree peel strength measured after 2 weeks of immersion, and the initial adhesive strength _F0 in the above formula is the above-described adhesive strength to SUS. The post-immersion adhesive strength F _B is more specifically measured by the method described in Examples below. The adhesive strength retention rate R _B is calculated from the post-immersion adhesive strength F _B and the initial adhesive strength F ₀ according to the above formula.

From the viewpoint of better suppressing the decrease in adhesive strength due to contact with an aqueous solvent (e.g., water, a lower alcohol, an aqueous solvent such as a mixed solvent of water and a lower alcohol), in some embodiments, the adhesive strength retention rate _RB is preferably 75% or more, more preferably 80% or more, further preferably 84% or more (e.g., 85% or more), may be 87% or more, or may be 90% or more. . The upper limit of the adhesive strength retention rate _RB is not particularly limited. The adhesive strength retention rate _RB is typically 100% or less, and from the viewpoint of compatibility with other properties (eg, initial adhesive strength F ₀ and oil resistance), in some embodiments, for example, 99 % or less, 98% or less, 96% or less, 95% or less, or 94% or less. In some aspects, from the viewpoint of bonding reliability against contact with an aqueous solvent, the post-immersion adhesive strength F _B is preferably 6.0 N/10 mm or more (eg, 6.5 N/10 mm or more). , More preferably 7.0 N / 10 mm or more (for example, 7.5 N / 10 mm), more preferably 8.0 N / 10 mm or more, may be 8.2 N / 10 mm or more, 8.5 N /10 mm or more, or 8.7 N/10 mm or more. The upper limit of the post-immersion adhesive strength F _B is not particularly limited. In some embodiments, from the viewpoint of compatibility with other properties (eg, initial adhesive strength F ₀ and aqueous solvent resistance), the post-immersion adhesive strength F _B may be, for example, 19 N/10 mm or less, and 18 N /10 mm or less, 17 N/10 mm or less, or 15 N/10 mm or less.

In some aspects, the pressure-sensitive adhesive sheet may contain a biomass-derived material and have a biomass-carbon ratio equal to or higher than a predetermined value. The biomass carbon ratio of the adhesive sheet is, for example, 1% or more, may be 10% or more, preferably 30% or more, and more preferably 50% or more. A high biomass carbon ratio of the pressure-sensitive adhesive sheet means that the amount of fossil resource-based materials such as petroleum used is small. From this point of view, the higher the biomass carbon ratio of the pressure-sensitive adhesive sheet, the better. For example, the biomass carbon ratio of the adhesive sheet may be 55% or more, 60% or more, 70% or more, 75% or more, 80% or more, or more than 80%. . The upper limit of the biomass carbon ratio is 100% by definition, and may be 99% or less. From the viewpoint of availability of materials, it may be 95% or less or 90% or less. From the viewpoint of facilitating good adhesion performance, in some embodiments, the biomass carbon ratio of the adhesive sheet may be, for example, 90% or less, 85% or less, or 80% or less.

<Application>
The use of the pressure-sensitive adhesive sheet disclosed herein is not particularly limited, and it can be used for various purposes. The pressure-sensitive adhesive sheet disclosed herein is preferably used for fixing various members that may come into contact with one or both of oil and aqueous solvents, taking advantage of the property of being able to achieve high adhesive strength, oil resistance, and aqueous solvent resistance at a high level. can be used. Typical examples of such uses include uses for fixing members in various types of mobile devices (portable devices). For example, it is suitable for fixing members in portable electronic devices. Non-limiting examples of the above portable electronic devices include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (for example, wrist wear type worn on the wrist like a wristwatch, Eyewear type including glasses type (monocular type and binocular type, including head-mounted type), clothes type attached to shirts, socks, hats, etc. in the form of accessories, earphones ear-wear type, etc.), digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game devices, electronic dictionaries, electronic notebooks, electronic books, vehicle-mounted information equipment, portable radios, portable televisions, portable printers, portable scanners, portable modems, etc. Non-limiting examples of portable devices other than portable electronic devices include mechanical watches, pocket watches, flashlights, hand mirrors, pass holders, and the like. In this specification, the term “portable” means not only being able to be simply carried, but also having a level of portability that allows an individual (a typical adult) to carry it relatively easily. shall mean.

FIG. 4 is an example schematically showing a portable electronic device (smartphone) using the adhesive sheet disclosed herein. As shown in FIG. 4 , a battery (heat generating element) 540 is built inside a housing 520 of the portable electronic device 500 . Moreover, the portable electronic device 500 is configured including an adhesive sheet 550 . In this configuration example, the adhesive sheet 550 has the form of a double-sided adhesive sheet (double-sided adhesive sheet) for fixing members constituting the portable electronic device 500 . The portable electronic device 500 includes a touch panel 570 whose display unit also functions as an input unit. The pressure-sensitive adhesive sheet disclosed herein is preferably used as a constituent element (member joining means) of the portable electronic device as described above.

In addition, the pressure-sensitive adhesive sheet disclosed herein, in some aspects, can have a pressure-sensitive adhesive layer containing an acrylic polymer with a high biomass carbon ratio, so a conventional general acrylic pressure-sensitive adhesive (i.e. , Acrylic adhesive with a low biomass carbon ratio) can be used as a substitute for the acrylic adhesive in various applications, thereby contributing to the suppression of dependence on fossil resource-based materials. The adhesive sheet disclosed herein can be preferably used as an adhesive sheet with reduced dependence on fossil resource-based materials.

Matters disclosed by this specification include the following.
[1] having a pressure-sensitive adhesive layer containing an acrylic polymer and a tackifying resin,
The acrylic polymer is a polymer of monomer components containing n-heptyl acrylate,
The content of the tackifying resin is an amount exceeding 10 parts by weight with respect to 100 parts by weight of the acrylic polymer,
The pressure-sensitive adhesive layer is a pressure-sensitive adhesive sheet having a degree of swelling of 100 or less with respect to ethyl acetate.
[2] The pressure-sensitive adhesive sheet according to [1] above, wherein the monomer component contains 5.0% by weight or more of a carboxy group-containing monomer.
[3] The pressure-sensitive adhesive sheet according to [1] or [2] above, wherein the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer contains an isocyanate-based cross-linking agent and an epoxy-based cross-linking agent in combination.
[4] The pressure-sensitive adhesive sheet according to any one of [1] to [3] above, wherein the pressure-sensitive adhesive layer contains a phenol-based tackifying resin as the tackifying resin.
[5] including a terpene phenol resin as the phenolic tackifying resin,
The pressure-sensitive adhesive sheet according to [4] above, wherein the content of the terpene phenol resin is 20 parts by weight or more with respect to 100 parts by weight of the acrylic polymer.
[6] The pressure-sensitive adhesive sheet according to any one of [1] to [5] above, wherein the acrylic polymer has a weight average molecular weight of more than 500,000.
[7] The pressure-sensitive adhesive sheet according to any one of [1] to [6] above, which has a 180 degree peel strength against a stainless steel plate of 8.0 N/10 mm or more.
[8] The pressure-sensitive adhesive sheet according to any one of [1] to [7] above, which is configured as a double-sided pressure-sensitive adhesive sheet.
[9] The above-described [1] to [1] to which are configured as a double-sided pressure-sensitive adhesive sheet having a resin film as a supporting substrate and the pressure-sensitive adhesive layer provided on one surface and the other surface of the supporting substrate. The pressure-sensitive adhesive sheet according to any one of [8].
[10] The pressure-sensitive adhesive sheet according to any one of [1] to [9] above, which is used for fixing a member in a portable device.

[11] A portable device comprising:
A pressure-sensitive adhesive sheet is bonded to a member constituting the electronic device,
The pressure-sensitive adhesive sheet has a pressure-sensitive adhesive layer containing an acrylic polymer and a tackifying resin,
The acrylic polymer is a polymer of monomer components containing n-heptyl acrylate,
The content of the tackifying resin is an amount exceeding 10 parts by weight with respect to 100 parts by weight of the acrylic polymer,
The portable device, wherein the pressure-sensitive adhesive layer has a degree of swelling of 100 or less with respect to ethyl acetate.
[12] The mobile device according to [11] above, wherein the mobile device is a mobile electronic device.
[13] The mobile device according to [11] or [12] above, wherein the monomer component of the acrylic polymer contains 5.0% by weight or more of a carboxy group-containing monomer.
[14] The mobile phone according to any one of [11] to [13] above, wherein the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer contains a combination of an isocyanate-based cross-linking agent and an epoxy-based cross-linking agent. device.
[15] The portable device according to any one of [11] to [14] above, wherein the pressure-sensitive adhesive layer contains a phenol-based tackifying resin as the tackifying resin.
[16] including a terpene phenol resin as the phenolic tackifying resin,
The mobile device according to [15] above, wherein the content of the terpene phenol resin is 20 parts by weight or more with respect to 100 parts by weight of the acrylic polymer.
[17] The mobile device according to any one of [11] to [16] above, wherein the acrylic polymer has a weight average molecular weight of more than 500,000.
[18] The portable device according to any one of [11] to [17] above, wherein the pressure-sensitive adhesive sheet has a 180-degree peel strength against a stainless steel plate of 8.0 N/10 mm or more.
[19] The portable device according to any one of [11] to [18] above, which is configured as a double-sided adhesive sheet.
[20] The pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet having a resin film as a supporting substrate and the pressure-sensitive adhesive layers provided on one surface and the other surface of the supporting substrate. The mobile device according to any one of [11] to [19] above.

Several examples relating to the present invention are described below, but the present invention is not intended to be limited to those shown in such examples. In the following description, "parts" and "%" are by weight unless otherwise specified.

<Evaluation method>
(Initial adhesive force F ₀ )
Under the measurement environment of 23° C. and 50% RH, a PET film having a thickness of 50 μm is adhered to one adhesive surface of the adhesive sheet (double-sided adhesive sheet) for lining, and the sheet is cut into a size of 10 mm in width and 100 mm in length. Prepare a measurement sample.
In an environment of 23° C. and 50% RH, the other adhesive surface of the measurement sample is pressed against the surface of a stainless steel plate (SUS304BA plate) washed with ethyl acetate by reciprocating a 2 kg roller once. After leaving it under the same environment for 30 minutes, using a tensile tester, according to JIS Z 0237: 2000, peel strength (initial adhesive strength F ₀ ) Measure [N/10 mm].

(Oil resistance)
Under the measurement environment of 23° C. and 50% RH, a PET film having a thickness of 50 μm is adhered to one adhesive surface of the adhesive sheet (double-sided adhesive sheet) for lining, and the sheet is cut into a size of 10 mm in width and 100 mm in length. Prepare a measurement sample.
In an environment of 23° C. and 50% RH, the other adhesive surface of the measurement sample is pressed against the surface of a stainless steel plate (SUS304BA plate) washed with ethyl acetate by reciprocating a 2 kg roller once. After leaving it in the same environment for 30 minutes, it is immersed in an oleic acid bath and kept in an environment of 40° C. and 90% RH for 2 weeks. After that, the measurement sample was pulled up from the oleic acid bath, the oleic acid adhering to the surroundings was lightly wiped off, and the sample was left in an environment of 23°C and 50% RH for 30 minutes. 2000, the peel strength after immersion in oleic acid (post-immersion adhesive force F _A ) [N/10 mm] is measured under the conditions of a tensile speed of 150 mm/min and a peel angle of 180 degrees.
From the obtained measurements, the following formula:
Adhesive force retention rate _RA [%] = (adhesive force after immersion F _A / initial adhesive force F ₀ ) × 100;
Calculate the adhesive strength retention rate _RA .

(Aqueous solvent resistance)
Peel strength after immersion in an aqueous solvent ₍ post-immersion adhesive strength F _B ) [N/10 mm].
From the obtained measurements, the following formula:
Adhesive strength maintenance rate R _B [%] = (post-immersion adhesive strength F _B / initial adhesive strength F ₀ ) × 100;
Calculate the adhesive strength retention rate _RB .

(degree of swelling)
An adhesive sample of about 0.1 g (weight W _S1 ) is wrapped in a porous polytetrafluoroethylene membrane (weight W _S2 ) having an average pore size of 0.2 μm in the form of a purse, and the opening is tied with a string (weight W S ₃ ). As the porous polytetrafluoroethylene (PTFE) membrane, trade name "Nitoflon (registered trademark) NTF1122" (average pore size 0.2 μm, porosity 75%, thickness 85 μm) available from Nitto Denko Corporation or its equivalent. use the product. The packet is immersed in 50 mL of ethyl acetate and kept at room temperature (approximately 23° C.) for 7 days. Thereafter, the package is taken out, ethyl acetate adhering to the outer surface is wiped off, and the weight (W _S4 ) of the package is measured. The packet is then dried at 130° C. for 2 hours and the weight (Wg ₅ ) of the packet is determined. The degree of swelling of the pressure-sensitive adhesive layer is obtained by substituting each value into the following formula.
Degree of swelling = ( _WS4 - _WS2 - _WS3 ) / ( _WS5 - _WS2 - _WS3 )

<Example 1>
(Synthesis of acrylic polymer)
96 parts of n-heptyl acrylate (n-HpA) and 4 parts of acrylic acid (AA) as monomer components were placed in a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, a reflux condenser and a dropping funnel, and a polymerization solvent. and ethyl acetate were charged, and the mixture was stirred for 2 hours while nitrogen gas was introduced. After removing oxygen in the polymerization system in this manner, 0.2 parts of 2,2′-azobisisobutyronitrile (AIBN) was added as a polymerization initiator, and solution polymerization was carried out at 60° C. to 70° C. for 8 hours. to obtain a solution of the acrylic polymer (A1). The acrylic polymer (A1) had a weight average molecular weight (Mw) of 900,000. The above n-HpA is a compound having a biomass-derived heptyl group at the ester end, synthesized using biomass-derived heptyl alcohol.

(Preparation of adhesive composition)
100 parts of the acrylic polymer (A1), tackifier resin B (trade name "YS Polystar S145", manufactured by Yasuhara Chemical Co., Ltd., terpene phenol resin, softening point 145 ° C., hydroxyl value 70 to 110 mgKOH / g) 30 parts, isocyanate cross-linking A pressure-sensitive adhesive composition according to this example was prepared by stirring and mixing 3 parts of an agent (based on solid content; hereinafter the same) and 0.03 parts of an epoxy-based cross-linking agent. As the isocyanate-based cross-linking agent, Tosoh's trade name "Coronate L" (75% ethyl acetate solution of trimethylolpropane/tolylene diisocyanate trimer adduct) was used. As the epoxy-based cross-linking agent, The trade name “TETRAD-C” (1,3-bis(N,N-diglycidylaminomethyl)cyclohexane) manufactured by Mitsubishi Gas Chemical Company was used.

(Preparation of adhesive sheet)
Two 38 μm thick polyester release films (trade name “Diafoil MRF”, 38 μm thick, manufactured by Mitsubishi Chemical Corporation) were prepared. The pressure-sensitive adhesive composition was applied to the release surfaces of these release films and dried at 100° C. for 2 minutes to form a pressure-sensitive adhesive layer having a thickness of 19 μm. The pressure-sensitive adhesive layers formed on the two release films were laminated to the first and second surfaces of a 12 μm-thick PET film (trade name “Lumirror”, manufactured by Toray Industries, Inc.) as a substrate. . The release film was left on the adhesive layer as it was and used to protect the surface (adhesive surface) of the adhesive layer. Thus, a 50 μm-thick double-sided pressure-sensitive adhesive sheet with a substrate having both pressure-sensitive adhesive surfaces protected by the two polyester release films was obtained.

<Example 2>
In the preparation of the adhesive composition of Example 1, instead of the tackifier resin B, tackifier resin A (trade name "YS Polystar T115", manufactured by Yasuhara Chemical Co., Ltd., terpene phenol resin, softening point 115 ° C., hydroxyl value 60 mg KOH / g )It was used. A double-sided pressure-sensitive adhesive sheet with a substrate according to this example was produced in the same manner as in Example 1, except that the obtained pressure-sensitive adhesive composition was used.

<Examples 3 to 9>
A solution of an acrylic polymer (A2) was obtained in the same manner as in the synthesis of the acrylic polymer (A1), except that the monomer composition was changed to 94 parts of n-HpA and 6 parts of AA and the concentrations of the monomer components during polymerization were adjusted. rice field. A pressure-sensitive adhesive composition according to each example was prepared in the same manner as in Example 1 except that the acrylic polymer (A2) was used and the composition was changed to that shown in Table 1, and the pressure-sensitive adhesive composition was used to prepare each A double-sided pressure-sensitive adhesive sheet with a substrate according to the example was produced. As the tackifying resin C shown in Table 1, trade name "Pensel D125" (polymerized rosin pentaerythritol ester, softening point 125°C, hydroxyl value 34 mgKOH/g) manufactured by Arakawa Chemical Industries, Ltd. was used.

<Examples 10 to 12>
A solution of an acrylic polymer (A3) was obtained in the same manner as in the synthesis of the acrylic polymer (A1), except that the monomer composition was changed to 90 parts of n-HpA and 10 parts of AA and the concentrations of the monomer components during polymerization were adjusted. rice field. A pressure-sensitive adhesive composition according to each example was prepared in the same manner as in Example 1 except that the acrylic polymer (A3) was used and the composition was changed to that shown in Table 1, and the pressure-sensitive adhesive composition was used to prepare each A double-sided pressure-sensitive adhesive sheet with a substrate according to the example was produced.

<Comparative Examples 1 and 2>
A pressure-sensitive adhesive composition according to this example was prepared in the same manner as in Example 5, except that the amount of tackifying resin A used was 0 parts (Comparative Example 1) or 5 parts (Comparative Example 2). A double-sided pressure-sensitive adhesive sheet with a substrate according to this example was produced using the composition.

<Comparative Examples 3-4>
A solution of acrylic polymer (A4) was obtained basically in the same manner as the synthesis of acrylic polymer (A1) except that the monomer composition was changed to 90 parts of 2-ethylhexyl acrylate (2EHA) and 10 parts of AA. A pressure-sensitive adhesive composition according to each example was prepared in the same manner as in Example 1 except that the acrylic polymer (A4) was used and the composition was changed to that shown in Table 2, and the pressure-sensitive adhesive composition was used to prepare each A double-sided pressure-sensitive adhesive sheet with a substrate according to the example was produced.

<Comparative Example 5>
A solution of acrylic polymer (A5) was obtained basically in the same manner as the synthesis of acrylic polymer (A1) except that the monomer composition was changed to 95 parts of n-butyl acrylate (BA) and 5 parts of AA. A pressure-sensitive adhesive composition according to this example was prepared in the same manner as in Example 1, except that the acrylic polymer (A5) was used and the composition was changed to that shown in Table 2. A double-sided pressure-sensitive adhesive sheet with a substrate was produced.

Tables 1 and 2 show the outline and evaluation results of the pressure-sensitive adhesive sheets according to each example.

As shown in Table 1, the pressure-sensitive adhesive layers according to Examples 1 to 12 consisted of an acrylic polymer containing n-heptyl acrylate as a monomer component and an amount of adhesive exceeding 10 parts per 100 parts of the acrylic polymer. The swelling degree with respect to ethyl acetate was 100 or less. The pressure-sensitive adhesive sheets according to these examples had good initial adhesive strength F ₀ , adhesive strength retention rate _RA to oil, and adhesive strength retention rate _RB to aqueous solvent. In other words, the adhesive strength, oil resistance and aqueous solvent resistance were all achieved at high levels. The surface free energies γ of the adhesive layers according to Examples 1 to 12 were all within the range of 10 to 35 mJ/m ² .

On the other hand, the pressure-sensitive adhesive sheets of Comparative Example 1 containing no tackifying resin and Comparative Example 2 containing a small amount of tackifying resin had a low initial adhesive force _F0 . Comparative Examples 3 and 4 are examples using an acrylic polymer _which is a polymer of a monomer component containing 2EHA as a main component and does not contain n-heptyl acrylate. In Comparative Example 4 in which the content of the tackifying resin was increased, although the initial adhesive force _F0 was increased, the degree of swelling greatly exceeded 100, and the adhesive force retention ratio _RA against oil was clearly lowered. Comparative Example 5 does not contain n-heptyl acrylate and uses an acrylic polymer, which is a polymer of monomer components containing BA as a main component, and has insufficient resistance to aqueous solvents.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

Reference Signs List 1, 2, 3 Adhesive sheet 10 Supporting substrate 10A First surface 10B Second surface (back surface)
21 adhesive layer (first adhesive layer)
21A adhesive surface (first adhesive surface)
21B second adhesive surface 22 adhesive layer (second adhesive layer)
22A adhesive surface (second adhesive surface)
31, 32 Release liner 100, 200, 300 PSA sheet with release liner

Claims (9)

having an adhesive layer containing an acrylic polymer and a tackifying resin,
The acrylic polymer is a polymer of monomer components containing 80% by weight or more of n-heptyl acrylate,
The monomer component contains 4.0% by weight or more of a carboxy group-containing monomer,
The content of the tackifying resin is an amount exceeding 10 parts by weight with respect to 100 parts by weight of the acrylic polymer,
The pressure-sensitive adhesive layer has a swelling degree with respect to ethyl acetate of 100 or less,
The pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer contains an isocyanate-based cross-linking agent,
The pressure-sensitive adhesive layer has a thickness of 35 μm or less,
A pressure-sensitive adhesive sheet having a 180-degree peel strength against a stainless steel plate of 8.0 N/10 mm or more . The pressure-sensitive adhesive sheet according to claim 1, wherein the monomer component contains 5.0% by weight or more of a carboxy group-containing monomer. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer contains a combination of the isocyanate-based cross-linking agent and the epoxy-based cross-linking agent. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the pressure-sensitive adhesive layer contains a phenol-based tackifying resin as the tackifying resin. including a terpene phenolic resin as the phenolic tackifying resin,
The adhesive sheet according to claim 4, wherein the content of said terpene phenol resin is 20 parts by weight or more with respect to 100 parts by weight of said acrylic polymer. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the acrylic polymer has a weight average molecular weight of more than 500,000. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the pressure-sensitive adhesive layer has a degree of swelling of 30 or more and 90 or less . 3. The double-sided pressure-sensitive adhesive sheet according to claim 1, comprising a resin film as a supporting substrate and the pressure-sensitive adhesive layers provided on one surface and the other surface of the supporting substrate. adhesive sheet. 3. The pressure-sensitive adhesive sheet according to claim 1, which is used for fixing a member in a mobile device.

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